WorldWideScience

Sample records for centimeter wavelength radio

  1. Possible radio precursors/signatures of the CMEs onset: radio type III bursts and fine structures in the centimeter-metric wavelength region

    International Nuclear Information System (INIS)

    Seventy-one occurrences of coronal mass ejections (CMEs) associated with radio bursts, seemingly associated with type III bursts/fine structures (FSs), in the centimeter-metric frequency range during 2003-2005, were obtained with the spectrometers at the National Astronomical Observatories, Chinese Academy of Sciences (NAOC) and the Culgoora radio spectrometer and are presented. The statistical results of 68 out of 71 events associated with the radio type III bursts or FSs during the initiation or early stages of the CMEs indicate that most CMEs contain the emissions of radio type III bursts/FSs near the time of the CME's onset, in spite of their fast or slow speeds. Therefore, we propose that type III bursts and FSs are possible precursors of the onset of CMEs. We stress that the radio type III bursts/FSs in the centimeter-metric wavelength region and the CME transients possibly occurred in conjunction with the origin of the coronal precursor structures. Thus, the statistical results support the suggestions that type III bursts/FSs are indicators of extra energy input into the corona at the CMEs' onset, and that the type III bursts/FSs are produced primarily due to a coronal instability which eventually triggers the CME process. This may signify that the centimeter-metric radio bursts corresponding to or near the CME's onset are caused by the disturbed corona (possibly including minor magnetic reconnections).

  2. Callisto - Disk temperature at 3.71-centimeter wavelength

    Science.gov (United States)

    Berge, G. L.; Muhleman, D. O.

    1975-01-01

    We observed the radio emission of Callisto with a three-element interferometer at the time of the 1973 opposition of Jupiter. Special care was taken to remove the residual, unresolved contribution from Jupiter itself in the antenna side lobes. The resulting disk temperature at a wavelength of 3.71 centimeters, assuming a radius of 2500 + or - 75 kilometers for Callisto, was 101 + or - 25 K. This temperature is much more consistent with emission from a simple dielectric sphere than the considerably higher temperatures that have been reported for wavelengths of 3.5 and 8.2 millimeters.

  3. Radio range measurements of coronal electron densities at 13 and 3.6 centimeter wavelengths during the 1985 solar conjunction of Voyager 2

    Science.gov (United States)

    Anderson, John D.; Krisher, Timothy P.; Borutzki, Susan E.; Connally, Michael J.; Eshe, Paula M.; Hotz, Henry B.; Kinslow, Scott; Kursinski, Emil R.; Light, Luann Brown; Matousek, Steven E.; Moyd, Katherine I.; Roth, Duane C.; Sweetnam, Donald N.; Taylor, Anthony H.; Tyler, G. Leonard; Gresh, Donna L.; Rosen, Paul A.

    1987-12-01

    Radio range measurements were generated by the Deep Space Network at two wavelengths (3.6 and 13 cm) during the solar conjunction of the Voyager 2 spacecraft in 1985 December. The difference in range at the two wavelengths provides a direct measurement of the integrated electron density along the ray path between Earth stations and the spacecraft. Derived electron density profiles on ingress and egress between 7 and 40 solar radii revealed a surprising asymmetry in the radial power-law dependence of the coronal electron density.

  4. Radio range measurements of coronal electron densities at 13 and 3.6 centimeter wavelengths during the 1988 solar conjunction of Voyager 2

    Science.gov (United States)

    Krisher, T. P.; Anderson, J. D.; Morabito, D. D.; Asmar, S. W.; Borutzki, S. E.; Delitsky, M. L.; Densmore, A. C.; Eshe, P. M.; Lewis, G. D.; Maurer, M. J.; Roth, D. C.; Son, Y. H.; Spilker, T. R.; Sweetnam, D. N.; Taylor, A. H.; Tyler, G. L.; Gresh, D. L.; Rosen, P. A.

    1991-07-01

    Radio range measurements of total solar plasma delay obtained during the solar conjunction of the Voyager 2 spacecraft in December 1988, which occurred near solar maximum activity in the 11 yr cycle are reported. The radio range measurements were generated by the Deep Space Network at two wavelengths on the downlink from the spacecraft: 3.6 and 13 cm. A direct measurement of the integrated electron density along the ray path between the earth stations and the spacecraft was obtained by differencing the range at the two wavelengths. Coronal electron density profiles have been derived during ingress and egress of the ray path, which approached the sun to within 5 solar radii. At 10 solar radii, the derived density profiles yield 34079 + or - 611/cu cm on ingress and 49688 + or - 983/cu cm on egress. These density levels are significantly higher than observed near previous solar maxima.

  5. 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.

  6. Galactic latitude dependence of centimeter-wavelength flicker

    International Nuclear Information System (INIS)

    Small-amplitude flickering of the flux density of extragalactic radio sources has been found at 9 cm by Heeschen (1984). It that paper, it was concluded that there was no apparent dependence of the flicker on Galactic latitude. Here, all the pertinent 9 cm data are reanalyzed, and it is found that flicker amplitude does show a latitude dependence consistent with that expected from interstellar scintillation. 7 references

  7. The radio environment of the 21 Centimeter Array: RFI detection and mitigation

    OpenAIRE

    Huang, Yan; Wu, Xiang-Ping; Zheng, Qian; Gu, Jun-Hua; Xu, Haiguang

    2016-01-01

    Detection and mitigation of radio frequency interference (RFI) is the first and also the key step for data processing in radio observations, especially for ongoing low frequency radio experiments towards the detection of the cosmic dawn and epoch of reionization (EoR). In this paper we demonstrate the technique and efficiency of RFI identification and mitigation for the 21 Centimeter Array (21CMA), a radio interferometer dedicated to the statistical measurement of EoR. For terrestrial, man-ma...

  8. Radio Wavelength Transients: Current and Emerging Prospects

    OpenAIRE

    Lazio, J.

    2008-01-01

    Known classes of radio wavelength transients range from the nearby--stellar flares and radio pulsars--to the distant Universe--\\gamma-ray burst afterglows. Hypothesized classes of radio transients include analogs of known objects, e.g., extrasolar planets emitting Jovian-like radio bursts and giant-pulse emitting pulsars in other galaxies, to the exotic, prompt emission from \\gamma-ray bursts, evaporating black holes, and transmitters from other civilizations. A number of instruments and faci...

  9. Radius and brightness temperature observations of Titan at centimeter wavelengths by the Very Large Array

    Science.gov (United States)

    Jaffe, W.; Caldwell, J.; Owen, T.

    1980-01-01

    Brightness and radius measurements of the surface of Titan at 6, 2, and 1.3 cm wavelengths obtained with the Very Large Array radio interferometer are presented. Combined results for the three wavelengths indicate that the radius is 2400 + or - 250 km, implying a density of 2.4 + or - 0.7 g/cu cm, and that the brightness temperature is 87 + or - 9 K. The surface temperature may be somewhat higher if the emissivity is less than unity. The new data do not permit a choice between an inversion model for the atmosphere of Titan that predicts a surface temperature of 78 K and a model with both a stratospheric temperature inversion and a modest greenhouse effect that would increase the surface temperature by 10-40 K.

  10. The radio environment of the 21 Centimeter Array: RFI detection and mitigation

    CERN Document Server

    Huang, Yan; Zheng, Qian; Gu, Jun-Hua; Xu, Haiguang

    2016-01-01

    Detection and mitigation of radio frequency interference (RFI) is the first and also the key step for data processing in radio observations, especially for ongoing low frequency radio experiments towards the detection of the cosmic dawn and epoch of reionization (EoR). In this paper we demonstrate the technique and efficiency of RFI identification and mitigation for the 21 Centimeter Array (21CMA), a radio interferometer dedicated to the statistical measurement of EoR. For terrestrial, man-made RFI, we concentrate mainly on a statistical approach by identifying and then excising non-Gaussian signatures, in the sense that the extremely weak cosmic signal is actually buried under thermal and therefore Gaussian noise. We also introduce the so-called visibility correlation coefficient instead of conventional visibility, which allows a further suppression of rapidly time-varying RFI. Finally, we briefly discuss removals of the sky RFI, the leakage of sidelobes from off-field strong radio sources with time-invarian...

  11. The radio environment of the 21 Centimeter Array: RFI detection and mitigation

    Science.gov (United States)

    Huang, Yan; Wu, Xiang-Ping; Zheng, Qian; Gu, Jun-Hua; Xu, Haiguang

    2016-02-01

    Detection and mitigation of radio frequency interference (RFI) is the first and also the key step for data processing in radio observations, especially for ongoing low frequency radio experiments towards the detection of the cosmic dawn and epoch of reionization (EoR). In this paper we demonstrate the technique and efficiency of RFI identification and mitigation for the 21 Centimeter Array (21CMA), a radio interferometer dedicated to the statistical measurement of EoR. For terrestrial, man-made RFI, we concentrate mainly on a statistical approach by identifying and then excising non-Gaussian signatures, in the sense that the extremely weak cosmic signal is actually buried under thermal and therefore Gaussian noise. We also introduce the so-called visibility correlation coefficient instead of conventional visibility, which allows a further suppression of rapidly time-varying RFI. Finally, we briefly discuss removals of the sky RFI, the leakage of sidelobes from off-field strong radio sources with time-invariant power and a featureless spectrum. It turns out that state of the art technique should allow us to detect and mitigate RFI to a satisfactory level in present low frequency interferometer observations such as those acquired with the 21CMA, and the accuracy and efficiency can be greatly improved with the employment of low-cost, high-speed computing facilities for data acquisition and processing.

  12. Radio Wavelength Observatories within the Exploration Architecture

    CERN Document Server

    Lazio, J; Burns, J; Demaio, L; Jones, D L; Weiler, K W

    2007-01-01

    Observations at radio wavelengths address key problems in astrophysics, astrobiology, and lunar structure including the first light in the Universe (the Epoch of Reionization), the presence of magnetic fields around extrasolar planets, particle acceleration mechanisms, and the structure of the lunar ionosphere. Moreover, achieving the performance needed to address these scientific questions demands observations at wavelengths longer than those that penetrate the Earth's ionosphere, observations in extremely "radio quiet" locations such as the Moon's far side, or both. We describe a series of lunar-based radio wavelength interferometers of increasing capability. The Radio Observatory for Lunar Sortie Science (ROLSS) is an array designed to be deployed during the first lunar sorties (or even before via robotic rovers) and addressing particle acceleration and the lunar ionosphere. Future arrays would be larger, more capable, and deployed as experience is gained in working on the lunar surface.

  13. Radio Sources in the NCP Region Observed with the 21 Centimeter Array

    CERN Document Server

    Zheng, Qian; Johnston-Hollitt, Melanie; Gu, Jun-Hua; Xu, Haiguang

    2016-01-01

    We present a catalog of 624 radio sources detected around the North Celestial Pole (NCP) with the 21 Centimeter Array (21CMA), a radio interferometer dedicated to the statistical measurement of the epoch of reionization (EoR). The data are taken from a 12 h observation made on 2013 April 13, with a frequency coverage from 75 to 175 MHz and an angular resolution of ~ 4 arcmin. The catalog includes flux densities at eight sub-bands across the 21CMA bandwidth and provides the in-band spectral indicies for the detected sources. To reduce the complexity of interferometric imaging from the so-called 'w' term and ionospheric effect, the present analyses are restricted to the east-west baselines within 1500 km only. The 624 radio sources are found within 5 degrees around the NCP down to ~ 10 mJy with a completeness of roughly 80%. Our source counts are compared, and also exhibit a good agreement with deep low-frequency observations made recently with the GMRT and MWA. In particular, for fainter radio sources below ~ ...

  14. Next Generation Very Large Array: Centimeter Radio Astronomy in the 2020s

    Science.gov (United States)

    Hughes, A. Meredith; Beasley, Anthony; Carilli, Christopher

    2015-08-01

    We discuss the future scientific discovery and technical challenges for cm radio studies, presenting calculations and simulations of the science of a next generation VLA (ngVLA), an array with vastly improved resolution and sensitivity relative to ALMA and JVLA, operating from ~1 GHz to 115 GHz, with an enhanced ability to image thermal objects on milliarcsecond scales, spanning thermal and non-thermal radio astronomy and bridging SKA and ALMA capabilities.Key areas of astrophysics where ngVLA can make new contributions include:- Probing deep into dusty protoplanetary disks, revealing terrestrial planet formation on AU-scales — regions that are opaque at shorter wavelengths. Observations in this wavelength range are critically required to study the poorly understood growth of dust into rocks.- Providing a census and imaging at kpc-scale resolution, of the cool molecular gas in distant galaxies. The ngVLA will be able to observe the lower order molecular transitions in high redshift, normal star forming galaxies, a key diagnostic for understanding the fuel driving the star formation history of the Universe.- Enabling an unprecedented, wide field imaging capability for nearby galaxies, over the cm frequency range covering key astrochemical tracers, including both thermal/non-thermal radio continuum emission.- Exploring the otherwise-unobservable deep atmospheres of the giant planets. In addition, the subsurfaces of other solar system bodies (e.g. icy satellites, TNOs, comets, asteroids) can be probed via thermal emission and radar remote sensing.- Allowing major improvements in synoptic, astrometric and transient/time-domain measurements at cm wavelengths of a wide variety of active sources, including Fast Radio Bursts, AGNs, pulsars and x-ray binaries.Led by NRAO, work to address the technical challenges for the ngVLA is underway. Areas currently under investigation include: low cost antennas, ultra-wide band feeds and receivers, broad band data transmission, and

  15. The FIRST Survey: Faint Images of the Radio Sky at Twenty Centimeters

    Science.gov (United States)

    Becker, Robert H.; White, Richard L.; Helfand, David J.

    1995-09-01

    The FIRST survey to produce Faint Images of the Radio Sky at Twenty centimeters is now underway using the NRAO Very Large Array. We describe here the scientific motivation for a large-area sky survey at radio frequencies which has a sensitivity and angular resolution comparable to the Palomar Observatory Sky Survey, and we recount the history that led to the current survey project. The technical design of the survey is covered in detail, including a description and justification of the grid pattern chosen, the rationale behind the integration time and angular resolution selected, and a summary of the other considerations which informed our planning for the project. A comprehensive description of the automated data analysis pipeline we have developed is presented. We also report here the results of the first year of FIRST observations. A total of 144 hr of time in 1993 April and May was used for a variety of tests, as well as to cover an initial strip of the survey extending between 07h 15m and 16h 30m in a 2°.8 wide declination zone passing through the local zenith (28.2 surface brightnesses well below our threshold. With 480 hr of observing time committed for each of the next three B-configuration periods, FIRST will complete nearly one-half of its goal of covering the 10,000 deg2 of the north Galactic cap scheduled for inclusion in the Sloan Digital Sky Survey. All of the FIRST data raw visibilities, self-calibrated UV data sets, individual pointing maps, final merged images, source catalogs, and individual source images are being placed in the public domain as soon as they are verified; all of the 1993 data are now available through the NRAO and/or the STScI archive. We conclude with a brief summary of the scientific significance of FIRST, which represents an improvement by a factor of 50 in both angular resolution and sensitivity over the best available large area radio surveys.

  16. Radio wavelength observations of the L134N molecular core

    International Nuclear Information System (INIS)

    A detailed study of the L134N dense molecular core through radio astronomical observations of spectral lines at millimeter and centimeter wavelengths is presented. The prototypical dark cloud was chosen for the following reasons: it is a nearby cloud at a distance of 160 pc, and thus radio observations have high spatial resolution; it resides out of the galactic disk, providing unobscured viewing along the line of sight; and it is known to be a rich source of molecular emission. The absence af any embedded infrared sources leads to the assumption that L134N is either in a stage of evolution prior to star formation or is a cloud in which internal support will prohibit a star from forming. A spectral line survey of 24 molecular transitions at up to seven positions in the L134N core, and observations of molecular emission from C18O, CSm, H13CO+, SO, NH3, and C3H2 are reviewed. Results indicate different spatial distributions for each species which may be attributed to variations in the excitation conditions for each transition or chemical abundance variations within the cloud core. Observational techniques and results are presented. 25 refs

  17. From Centimeter to Millimeter Wavelengths A High Angular Resolution Study of 3C273

    CERN Document Server

    Krichbaum, T P; Zensus, J A

    2001-01-01

    We monitored 3C273 with VLBI at 15-86 GHz since 1990. We discuss component trajectories, opacity effects at the jet base, a rotating and perhaps precessing jet, and outburst-ejection relations from Gamma-ray to radio bands.

  18. Large-scale features of the sun at 20 centimeter wavelength

    Science.gov (United States)

    Gopalswamy, N.; White, S. M.; Kundu, M. R.

    1991-01-01

    Results are reported from an experimental study of the characteristics of large-scale coronal structures such as active regions, plages, filaments, and coronal holes using data obtained with the VLA at 1.5 GHz during the period September 11-17, 1988. The radio data were supplemented with He 10830- A, H-alpha, and Calcium-K spectroheliograms. A statistical analysis of some of the characteristics of the active regions is performed. Most of the active region sources were found to be about 100 arcsec in size, with bridges between regions common; lower brightness temperature regions showed a higher degree of polarization in general. The maximum polarization was found at the edge of active regions but well within the associated plages. The degree of polarization from bright active regions was small (not more than 20 percent), in agreement with previous results. Evidence was found for compression of preexisting flux by the emerging flux from a new region, which took place in the apparent absence of magnetic reconnection.

  19. Extragalactic 1 millimeter sources - Simultaneous observations at centimeter, millimeter, and visual wavelengths

    Science.gov (United States)

    Landau, R.; Jones, T. W.; Epstein, E. E.; Neugebauer, G.; Soifer, B. T.; Werner, M. W.; Puschell, J. J.; Balonek, T. J.

    1983-01-01

    Observations simultaneously made at visual (B, V, and R) wavelengths, at 1, 1.4, and 3.4 mm and at 1.3, 2, 6, and 20 cm of 9 QSOs and BL Lac objects are reported. The range of the millimeter-visual spectral index alpha sub mv was only 0.65-0.82, typical of optically thin synchrotron emission. This may indicate that the electrons radiating synchrotron emission in this portion of the spectrum are not subjected to large radiation losses, and therefore relativistic bulk motion with Doppler factors of about 10 are required. The visual spectral index is much more broadly distributed and typically larger than alpha sub mv. The spectral energy distributions have not changed much in the last two to five years except for 2251+15 and perhaps 0235+164. Only 1749+09 shows a sharp spectral break shortward of 1 mm. Sixteen other sources were observed at 1 mm, of which seven were detected.

  20. The 60 micron to 20 centimeter infrared-to-radio ratio within spiral galaxies

    International Nuclear Information System (INIS)

    A detailed comparison is presented of the distribution of 60 micron IR and 20 cm radio continuum emission within 25 galaxies, mostly disk spirals. Local maxima in the thermal IR and nonthermal radio emission are found to be spatially coincident on scales of less than about 0.4 kpc in the nearest sample galaxies. The IR-red disk in normal spirals appears to be characterized by a shorter scale length than that of the radio continuum disk, suggesting that the IR-to-radio ratio should decrease as a function of radius. A model that successfully accounts for the observations is introduced which is based on the assumptions of steady-state star formation activity within the disk on kpc scales and a tight coupling between the origins of the dust-heating radiation and the radio-emitting cosmic-ray electrons. The underlying source is described as an exponential disk. The results also suggest that a random walk process cannot by itself describe the temporal evolution of cosmic rays. 34 refs

  1. Celestial Reference Frames at Multiple Radio Wavelengths

    Science.gov (United States)

    Jacobs, Christopher S.

    2012-01-01

    In 1997 the IAU adopted the International Celestial Reference Frame (ICRF) built from S/X VLBI data. In response to IAU resolutions encouraging the extension of the ICRF to additional frequency bands, VLBI frames have been made at 24, 32, and 43 gigahertz. Meanwhile, the 8.4 gigahertz work has been greatly improved with the 2009 release of the ICRF-2. This paper discusses the motivations for extending the ICRF to these higher radio bands. Results to date will be summarized including evidence that the high frequency frames are rapidly approaching the accuracy of the 8.4 gigahertz ICRF-2. We discuss current limiting errors and prospects for the future accuracy of radio reference frames. We note that comparison of multiple radio frames is characterizing the frequency dependent systematic noise floor from extended source morphology and core shift. Finally, given Gaia's potential for high accuracy optical astrometry, we have simulated the precision of a radio-optical frame tie to be approximately10-15 microarcseconds ((1-sigma) (1-standard deviation), per component).

  2. Detecting fast radio bursts at decametric wavelengths

    CERN Document Server

    Rajwade, Kaustubh

    2016-01-01

    Fast radio bursts (FRBs) are highly dispersed, sporadic radio pulses that are likely extragalactic in nature. Here we investigate the constraints on the source population from surveys carried out at frequencies $<1$~GHz. All but one FRB has so far been discovered in the 1--2~GHz band, but new and emerging instruments look set to become valuable probes of the FRB population at sub-GHz frequencies in the near future. In this paper, we consider the impacts of free-free absorption and multi-path scattering in our analysis via a number of different assumptions about the intervening medium. We consider previous low frequency surveys alongwith an ongoing survey with the University of Technology digital backend for the Molonglo Observatory Synthesis Telescope (UTMOST) as well as future observations with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and the Hydrogen Intensity and Real-Time Analysis Experiment (HIRAX). We predict that CHIME and HIRAX will be able to observe $\\sim$ 30 or more FRBs per da...

  3. Centimeter wavelength continuum observations of young stellar objects in the dark cloud DC 303.8-14.2

    NARCIS (Netherlands)

    Lehtinen, K; Higdon, JL

    2003-01-01

    We have made radio continuum observations with the ATCA (Australia Telescope Compact Array)* at 3 and 6 cm of the dark cloud DC 303.8-14.2 in order to study the content of young stellar objects (YSOs) in this cloud. Four unresolved sources were found within the cloud's boundary. One of these in coin

  4. Radio Recombination Lines at Decametre Wavelengths: Prospects for the Future

    CERN Document Server

    Peters, W M; Clarke, T E; Erickson, W C; Kassim, N E

    2010-01-01

    This paper considers the suitability of a number of emerging and future instruments for the study of radio recombination lines (RRLs) at frequencies below 200 MHz. These lines arise only in low-density regions of the ionized interstellar medium, and they may represent a frequency-dependent foreground for next-generation experiments trying to detect H I signals from the Epoch of Reionization and Dark Ages ("21-cm cosmology"). We summarize existing decametre-wavelength observations of RRLs, which have detected only carbon RRLs. We then show that, for an interferometric array, the primary instrumental factor limiting detection and study of the RRLs is the areal filling factor of the array. We consider the Long Wavelength Array (LWA-1), the LOw Frequency ARray (LOFAR), the low-frequency component of the Square Kilometre Array (SKA-lo), and a future Lunar Radio Array (LRA), all of which will operate at decametre wavelengths. These arrays offer digital signal processing, which should produce more stable and better ...

  5. SARAS measurement of the Radio Background at long wavelengths

    CERN Document Server

    Patra, Nipanjana; Sethi, Shiv; Shankar, N Udaya; Raghunathan, A

    2014-01-01

    SARAS is a correlation spectrometer connected to a frequency independent antenna that is purpose-designed for precision measurements of the radio background at long wavelengths. The design, calibration and observing strategies admit solutions for the internal additive contributions to the radiometer response, and hence a separation of these contaminants from the antenna temperature. We present here a wideband measurement of the radio sky spectrum by SARAS that provides an accurate measurement of the absolute brightness and spectral index between 110 and 175 MHz. Accuracy in the measurement of absolute sky brightness is limited by systematic errors of magnitude 1.2%; errors in calibration and in the joint estimation of sky and system model parameters are relatively smaller. We use this wide-angle measurement of the sky brightness using the precision wide-band dipole antenna to provide an improved absolute calibration for the 150-MHz all-sky map of Landecker & Wielebinski (1970):subtracting an offset of 21....

  6. RAPID INTRINSIC VARIABILITY OF SGR A* AT RADIO WAVELENGTHS

    International Nuclear Information System (INIS)

    Sgr A* exhibits flares in radio, millimeter, and submillimeter wavelengths with durations of ∼1 hr. Using structure function, power spectrum, and autocorrelation function analysis, we investigate the variability of Sgr A* on timescales ranging from a few seconds to several hours and find evidence for subminute timescale variability at radio wavelengths. These measurements suggest a strong case for continuous variability from subminute to hourly timescales. This short timescale variability constrains the size of the emitting region to be less than 0.1 AU. Assuming that the minute timescale fluctuations of the emission at 7 mm arise through the expansion of regions of optically thick synchrotron-emitting plasma, this suggests the presence of explosive, energetic expansion events at speeds close to c. The required rates of mass processing and energy loss of this component are estimated to be ∼>6 x 10-10 Msun yr-1 and 400 Lsun, respectively. The inferred scale length corresponding to 1 minute light travel time is comparable to the time-averaged spatially resolved 0.1 AU scale observed at 1.3 mm emission of Sgr A*. This steady component from Sgr A* is interpreted mainly as an ensemble average of numerous weak and overlapping flares that are detected on short timescales. The nature of such short timescale variable emission or quiescent variability is not understood but could result from fluctuations in the accretion flow of Sgr A* that feed the base of an outflow or jet.

  7. 21 centimeter HI absorption at z = 0.437 against the extended radio structure of 3c 196

    International Nuclear Information System (INIS)

    We report the detection of an absorption line at 988.7. MHz toward the quasar 3C 196. We identify this line as the lambda21 cm line of neutral atomic hydrogen seen at a redshift of z/sub abs/ = 0.4366. No optical absorption lines have been noted in the z/sub em/ = 0.871 quasar 3C 196 heretofore. All the radio emission of 3C 196 is contained in two thetaroughly-equal3'' extended lobes symmetrically placed (position angle approx.260) about the optical object. The optical QSO itself is an extremely weak, 0, that is in a direction perpendicular to the separation of the radio lobes. If this wisp is the disk of an intervening galaxy, then the H i absorption is direct evidence for absorption in a galactic halo. Puzzles abound; (1) If the optical wisp seen superposed on the QSO is an intervening galaxy then what aspects, if any, of the emission from 3C 196 are gravitational lens effects. (2) If the wisp is associated with the QSO, why is it radio quiet and why is it orthogonal to the extended radio structure of 3C 196. (3) Is it significant that z/sub abs/ is one-half z/sub em/ within the errors

  8. Cryogenically cooled low-noise amplifier for radio-astronomical observations and centimeter-wave deep-space communications systems

    Science.gov (United States)

    Vdovin, V. F.; Grachev, V. G.; Dryagin, S. Yu.; Eliseev, A. I.; Kamaletdinov, R. K.; Korotaev, D. V.; Lesnov, I. V.; Mansfeld, M. A.; Pevzner, E. L.; Perminov, V. G.; Pilipenko, A. M.; Sapozhnikov, B. D.; Saurin, V. P.

    2016-01-01

    We report a design solution for a highly reliable, low-noise and extremely efficient cryogenically cooled transmit/receive unit for a large antenna system meant for radio-astronomical observations and deep-space communications in the X band. We describe our design solution and the results of a series of laboratory and antenna tests carried out in order to investigate the properties of the cryogenically cooled low-noise amplifier developed. The transmit/receive unit designed for deep-space communications (Mars missions, radio observatories located at Lagrangian point L2, etc.) was used in practice for communication with live satellites including "Radioastron" observatory, which moves in a highly elliptical orbit.

  9. Spectral line broadening of decimeter and centimeter radio waves during radio communication through near-solar plasma with the Venera-15,16 space probes

    International Nuclear Information System (INIS)

    Results of data analysis on spectral line broadening of decimeter (λ=32 cm) and centimeter (λ=5 cm) radiosignals of the 'Venera-15,16' probes in the process of their propagation through near-solar plasma are presented. It is shown that the width of decimeter radiowave spectral line increases in case of single propagation of the radiowaves from 0.2 Hz, when the distance of beam line from the Sun is 30 solar radii R0, up to 600 Hz in case of the beam line removal by 2.5 R0. In case of double pass of the radiowaves the spectral line broadening increases 2.5-4-fold as compared with the case of single propagation. It is ascertained that frequency dependence of the spectral line width is dose to root-mean-square law for impact distances between 8 and 2.5 R0, and in certain cases it is much stronger

  10. 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...

  11. Unusual Solar Radio Burst Observed at Decameter Wavelengths

    CERN Document Server

    Melnik, V N; Konovalenko, A A; Rucker, H O; Frantsuzenko, A V; Dorovskyy, V V; Panchenko, M; Stanislavskyy, A A

    2015-01-01

    An unusual solar burst was observed simultaneously by two decameter radio telescopes UTR-2 (Kharkov, Ukraine) and URAN-2 (Poltava, Ukraine) on 3 June 2011 in the frequency range 16-28 MHz. The observed radio burst has some unusual properties, which are not typical for the other types of solar radio bursts. The frequency drift rate of it was positive (about 500 kHz s$^{-1}$) at frequencies higher than 22 MHz and negative (100 kHz s$^{-1}$) at lower frequencies. The full duration of this event varies from 50 s up to 80 s, depending on the frequency. The maximum radio flux of the unusual burst reaches $\\approx 10^3$ s.f.u and its polarization does not exceed 10%. This burst has a fine frequency-time structure of unusual appearance. It consists of stripes with the frequency bandwidth 300-400 kHz. We consider that several accompanied radio and optical events observed by SOHO and STEREO spacecraft are possibly associated with the reported radio burst. A model that may interpret the observed unusual solar radio burs...

  12. Multi-Timescale Radio Observations of Multi-Wavelength GRBs

    Science.gov (United States)

    Van der Horst, Alexander

    2016-07-01

    Gamma-ray bursts are a broadband phenomenon, with emission detected across the electromagnetic spectrum from low-frequency radio waves to high-energy gamma-rays. Besides this extremely broad spectral range, they are also observed over a very large range of timescales, from millisecond variability in gamma-rays to the afterglows at radio frequencies that can sometimes be observed for years after the initial gamma-ray trigger. Our current understanding of gamma-ray bursts is based on these multi-frequency and multi-timescale observations. In this talk I will show the role that radio observations have played and will play in putting together a broadband picture of the physics behind the observed emission, the progenitors, and their environment. I will highlight some recent discoveries and developments, in particular the searches for early radio emission within the first minutes after gamma-ray triggers; the increasing number of radio-detected, optically dark bursts; and the possibilities that several new and upgraded radio observatories offer to obtain a better understanding of the macro- and microphysics behind these enigmatic phenomena.

  13. Direct evidence for solar wind control of Jupiter's hectometer-wavelength radio emission

    Science.gov (United States)

    Desch, M. D.; Barrow, C. H.

    1984-01-01

    Observations of the solar wind close to Jupiter by the Voyager 1 and Voyager 2 spacecraft in 1978 and 1979 are compared with the hectometer-wavelength radio emission from the planet. A significant positive correlation is found between variations in the solar wind plasma density at Jupiter and the level of Jovian radio emission output. During the 173-day interval studied for the Voyager 2 data the radio emission displayed a long-term periodicity of about 13 days, identical to that shown by the solar wind density at Jupiter and consistent with the magnetic sector structure association already proposed for ground-based observations of the decameter-wavelength emission.

  14. The radio continuum spectrum of Mira A and Mira B up to submillimeter wavelengths

    CERN Document Server

    Planesas, Pere; Bachiller, Rafael

    2016-01-01

    We present new measurements of the flux densities at submillimeter wavelengths based on ALMA band 7 (338 GHz) and band 9 (679 GHz) observations to better constrain the origin of the continuum emission of the Mira AB binary system and to check its orbit. We have measured the Mira A and Mira B continuum in ALMA band 7, with a resolution of ~0"31, and for the first time in ALMA band 9, with a resolution of ~0"18. We resolved the binary system at both bands, and derived the continuum spectral index of the stars and their relative position. We also analyzed ALMA SciVer data obtained in bands 6 and 3. Measurements at centimeter wavelengths obtained by other authors have been included in our study of the spectral energy distribution of the Mira components. The Mira A continuum emission has a spectral index of 1.98+-0.04 extending from submillimeter down to centimeter wavelengths. The spectral index of the Mira B continuum emission is 1.93+-0.06 at wavelengths ranging from submillimeter to ~3.1 mm, and a shallower sp...

  15. A wide-band, active antenna system for long wavelength radio astronomy

    CERN Document Server

    Hicks, Brian C; Stewart, Kenneth P; Erickson, William C; Ray, Paul S; Kassim, Namir E; Burns, Steve; Clarke, Tracy; Schmitt, Henrique; Craig, Joe; Hartman, Jake; Weiler, Kurt W

    2012-01-01

    We describe an "active" antenna system for HF/VHF (long wavelength) radio astronomy that has been successfully deployed 256-fold as the first station (LWA1) of the planned Long Wavelength Array. The antenna system, consisting of crossed dipoles, an active balun/preamp, a support structure, and a ground screen has been shown to successfully operate over at least the band from 20 MHz (15 m wavelength) to 80 MHz (3.75 m wavelength) with a noise figure that is at least 6 dB better than the Galactic background emission noise temperature over that band. Thus, the goal to design and construct a compact, inexpensive, rugged, and easily assembled antenna system that can be deployed many-fold to form numerous large individual "stations" for the purpose of building a large, long wavelength synthesis array telescope for radio astronomical and ionospheric observations was met.

  16. The faint radio source population at 15.7 GHz - II. Multi-wavelength properties

    CERN Document Server

    Whittam, I H; Green, D A; Jarvis, M J; Vaccari, M

    2015-01-01

    A complete, flux density limited sample of 96 faint ($> 0.5$ mJy) radio sources is selected from the 10C survey at 15.7 GHz in the Lockman Hole. We have matched this sample to a range of multi-wavelength catalogues, including SERVS, SWIRE, UKIDSS and optical data; multi-wavelength counterparts are found for 80 of the 96 sources and spectroscopic redshifts are available for 24 sources. Photometric reshifts are estimated for the sources with multi-wavelength data available; the median redshift of the sample is 0.91 with an interquartile range of 0.84. Radio-to-optical ratios show that at least 94 per cent of the sample are radio loud, indicating that the 10C sample is dominated by radio galaxies. This is in contrast to samples selected at lower frequencies, where radio-quiet AGN and starforming galaxies are present in significant numbers at these flux density levels. All six radio-quiet sources have rising radio spectra, suggesting that they are dominated by AGN emission. These results confirm the conclusions o...

  17. The R Aquarii-jet at UV and radio wavelengths

    Science.gov (United States)

    Michalitsianos, A. G.; Kafatos, M.; Hollis, J. M.

    1986-01-01

    The jet and central star of the peculiar symbiotic variable R Aquarii was monitored with IUE low resolution SWP 1200 to 2000 A spectra, in order to detect possible temporal variations. The absolute line intensities of N V, C IV and He II, as well as numerous other ionic species in the jet are found to vary on a timescale of 1.5 yr. High spatial resolution radio VLA maps and SiO maser millimeter interferometer observations of the star are quoted.

  18. Extragalactic radio sources with sharply inverted spectrum at metre wavelengths

    CERN Document Server

    Gopal-Krishna,; Mhaskey, Mukul; Ranadive, Pritesh; Wiita, Paul J; Goyal, A; Kantharia, N G; Ishwara-Chandra, C H

    2014-01-01

    We present the first results of a systematic search for the rare extragalactic radio sources showing an inverted (integrated) spectrum, with spectral index $\\alpha \\ge +2.0$, a previously unexplored spectral domain. The search is expected to yield strong candidates for $\\alpha \\ge +2.5$, for which the standard synchrotron self-absorption (characterized by a single power-law energy distribution of relativistic electron population) would not be a plausible explanation, even in an ideal case of a perfectly homogeneous source of incoherent synchrotron radiation. Such sharply inverted spectra, if found, would require alternative explanations, e.g., free-free absorption, or non-standard energy distribution of relativistic electrons which differs from a power-law (e.g., Maxwellian). The search was carried out by comparing two sensitive low-frequency radio surveys made with sub-arcminute resolution, namely, the WISH survey at 352 MHz and TGSS/DR5 at 150 MHz. The overlap region between these two surveys contains 7056 ...

  19. On the abundance of gravitational arcs produced by submillimeter galaxies at radio and submm wavelengths

    CERN Document Server

    Fedeli, C

    2009-01-01

    We predict the abundance of giant gravitational arcs produced by submillimeter galaxies (SMGs) lensed by foreground galaxy clusters, both at radio and submm wavelengths. The galaxy cluster population is modeled in a realistic way with the use of semi-analytic merger trees, while the density profiles of individual deflectors take into account ellipticity and substructures. The adopted typical size of the radio and submm emitting regions of SMGs is based on current radio/CO observations and the FIR-radio correlation. The source redshift distribution has been modeled using three different functions (based on spectroscopic/photometric redshift measurements and a simple evolutionary model) to quantify the effect of a high redshift tail on the number of arcs. The source number counts are compatible with currently available observations, and were suitably distorted to take into account the lensing magnification bias. We present tables and plots for the numbers of radio and submm arcs produced by SMGs as a function o...

  20. Mars' radio spectrum and the flying dust.

    NARCIS (Netherlands)

    M. Roos-Serote; D.M. Stam; R.P. Fender

    2004-01-01

    Mars' radio spectrum at centimeter wavelengths is produced by thermal radiation from the surface and sub-surface. Observations at 2.8 cm made in the 1975 and 1978 show variations of its radio brightness as a function of longitude on the planet (Doherty et al. , ApJ 233, 1979). In addition, an overal

  1. Radio frequency controlled synthetic wavelength sweep for absolute distance measurement by optical interferometry

    International Nuclear Information System (INIS)

    We present a new technique applied to the variable optical synthetic wavelength generation in optical interferometry. It consists of a chain of optical injection locking among three lasers: first a distributed-feedback laser is used as a master to injection lock an intensity-modulated laser that is directly modulated around 15 GHz by a radio frequency generator on a sideband. A second distributed-feedback laser is injection locked on another sideband of the intensity-modulated laser. The variable synthetic wavelength for absolute distance measurement is simply generated by sweeping the radio frequency over a range of several hundred megahertz, which corresponds to the locking range of the two slave lasers. In this condition, the uncertainty of the variable synthetic wavelength is equivalent to the radio frequency uncertainty. This latter has a relative accuracy of 10-7 or better, resulting in a resolution of ±25 μm for distances exceeding tens of meters. The radio frequency generator produces a linear frequency sweep of 1 ms duration (i.e., exactly equal to one absolute distance measurement acquisition time), with frequency steps of about 1 MHz. Finally, results of absolute distance measurements for ranges up to 10 m are presented

  2. Radio frequency controlled synthetic wavelength sweep for absolute distance measurement by optical interferometry.

    Science.gov (United States)

    Le Floch, Sébastien; Salvadé, Yves; Mitouassiwou, Rostand; Favre, Patrick

    2008-06-01

    We present a new technique applied to the variable optical synthetic wavelength generation in optical interferometry. It consists of a chain of optical injection locking among three lasers: first a distributed-feedback laser is used as a master to injection lock an intensity-modulated laser that is directly modulated around 15 GHz by a radio frequency generator on a sideband. A second distributed-feedback laser is injection locked on another sideband of the intensity-modulated laser. The variable synthetic wavelength for absolute distance measurement is simply generated by sweeping the radio frequency over a range of several hundred megahertz, which corresponds to the locking range of the two slave lasers. In this condition, the uncertainty of the variable synthetic wavelength is equivalent to the radio frequency uncertainty. This latter has a relative accuracy of 10(-7) or better, resulting in a resolution of +/-25 microm for distances exceeding tens of meters. The radio frequency generator produces a linear frequency sweep of 1 ms duration (i.e., exactly equal to one absolute distance measurement acquisition time), with frequency steps of about 1 MHz. Finally, results of absolute distance measurements for ranges up to 10 m are presented. PMID:18516123

  3. 3.3 cm JVLA observations of transitional disks: searching for centimeter pebbles

    CERN Document Server

    Zapata, Luis A; Palau, Aina

    2016-01-01

    We present sensitive (rms-noises $\\sim$ 4 -- 25 $\\mu$Jy) and high angular resolution ($\\sim$1--2$"$) 8.9 GHz (3.3 cm) Karl G. Jansky Very Large Array (JVLA) radio continuum observations of 10 presumed transitional disks associated with young low-mass stars. We report the detection of radio continuum emission in 5 out of the 10 objects (RXJ1615, UX Tau A, LkCa15, RXJ1633, and SR24s). In the case of LkCa15, the centimeter emission is extended, and has a similar morphology to that of the transitional disk observed at mm wavelengths with an inner depression. For these five detections, we construct the Spectral Energy Distributions (SEDs) from the centimeter to submillimeter wavelengths, and find that they can be well fitted with a single (RXJ 1633 and UX Tau A) or a two component power-law (LkCa 15, RXJ 1615, and SR24s). For the cases where a single power-law fits well the data, the centimeter emission is likely produced by optically thin dust with large grains i.e. centimeter-size pebbles) present in the transit...

  4. Detection of the AM Her type cataclysmic variable V834 Cen at radio wavelengths

    International Nuclear Information System (INIS)

    The first detection is reported of the AM Her type cataclysmic variable system V834 Cen at 8.4 GHz, making it the second AM Her system to be detected at radio wavelengths. The radio emission is variable on time-scales as short as 1 min and reaches peak flux densities of 35 mJy. Longer time-scale variations of order of tens of minutes and levels of 12 mJy may be correlated with binary phase. The emission mechanism is probably an electron-cyclotron maser. (author)

  5. Solar longitude dependence of some characteristics of type III radio bursts from metric to hectometric wavelengths

    Science.gov (United States)

    Sakurai, K.

    1974-01-01

    Using the observed data for metric and hectometric type III radio bursts, the dependence of burst characteristics on the solar longitude has been examined over a wide frequency range. It is found that there exists and east-west asymmetry for the extension of metric type III bursts into the hectometric wavelength range. In particular, hectometric bursts are rarely observed for solar flares associated with metric bursts east of 60 E solar longitude. Furthermore, for east longitudes, the low-frequency radio observations show a large dispersion in drift time interval.

  6. MULTI-WAVELENGTH RADIO CONTINUUM EMISSION STUDIES OF DUST-FREE RED GIANTS

    International Nuclear Information System (INIS)

    Multi-wavelength centimeter continuum observations of non-dusty, non-pulsating K spectral-type red giants directly sample their chromospheres and wind acceleration zones. Such stars are feeble emitters at these wavelengths, however, and previous observations have provided only a small number of modest signal-to-noise measurements slowly accumulated over three decades. We present multi-wavelength Karl G. Jansky Very Large Array thermal continuum observations of the wind acceleration zones of two dust-free red giants, Arcturus (α Boo: K2 III) and Aldebaran (α Tau: K5 III). Importantly, most of our observations of each star were carried out over just a few days, so that we obtained a snapshot of the different stellar atmospheric layers sampled at different wavelengths, independent of any long-term variability. We report the first detections at several wavelengths for each star including a detection at 10 cm (3.0 GHz: S band) for both stars and a 20 cm (1.5 GHz: L band) detection for α Boo. This is the first time single (non-binary) luminosity class III red giants have been detected at these continuum wavelengths. Our long-wavelength data sample the outer layers of α Boo's atmosphere where its wind velocity is approaching (or possibly has reached) its terminal value and the ionization balance is becoming frozen-in. For α Tau, however, our long-wavelength data are still sampling its inner atmosphere, where the wind is still accelerating probably due to its lower mass-loss rate. We compare our data with published semi-empirical models based on ultraviolet data, and the marked deviations highlight the need for new atmospheric models to be developed. Spectral indices are used to discuss the possible properties of the stellar atmospheres, and we find evidence for a rapidly cooling wind in the case of α Boo. Finally, we develop a simple analytical wind model for α Boo based on our new long-wavelength flux measurements

  7. Ghostly Glow Reveals a Hidden Class of Long-Wavelength Radio Emitters

    Science.gov (United States)

    2008-10-01

    (Washington, DC. 08)- A team of scientists, including astronomers from the Naval Research Laboratory (NRL), have detected long wavelength radio emission from a colliding, massive galaxy cluster which, surprisingly, is not detected at the shorter wavelengths typically seen in these objects. The discovery implies that existing radio telescopes have missed a large population of these colliding objects. It also provides an important confirmation of the theoretical prediction that colliding galaxy clusters accelerate electrons and other particles to very high energies through the process of turbulent waves. The team revealed their findings in the October 16, 2008 edition of Nature. This new population of objects is most easily detected at long wavelengths. Professor Greg Taylor of the University of New Mexico and scientific director of the Long Wavelength Array (LWA) points out, "This result is just the tip of the iceberg. When an emerging suite of much more powerful low frequency telescopes, including the LWA in New Mexico, turn their views to the cosmos, the sky will 'light up' with hundreds or even thousands of colliding galaxy clusters." NRL has played a key role in promoting the development of this generation of new instruments and is currently involved with the development of the LWA. NRL radio astronomer and LWA Project Scientist Namir Kassim says "Our discovery of a previously hidden class of low frequency cluster-radio sources is particularly important since the study of galaxy clusters was a primary motivation for development of the LWA." The discovery of the emission in the galaxy cluster Abell 521 (or A521 for short) was made using the Giant Metrewave Radiotelescope (GMRT) in India, and its long wavelength nature was confirmed by the National Science Foundation's (NRAO) Very Large Array (VLA) radio telescope in New Mexico. The attached image shows the radio emission at a wavelength of 125cm in red superimposed on a blue image made from data taken by the

  8. Simultaneous absolute timing of the Crab pulsar at radio and optical wavelengths

    Science.gov (United States)

    Oosterbroek, T.; Cognard, I.; Golden, A.; Verhoeve, P.; Martin, D. D. E.; Erd, C.; Schulz, R.; Stüwe, J. A.; Stankov, A.; Ho, T.

    2008-09-01

    Context: The Crab pulsar emits across a large part of the electromagnetic spectrum. Determining the time delay between the emission at different wavelengths will allow to better constrain the site and mechanism of the emission. We have simultaneously observed the Crab Pulsar in the optical with S-Cam, an instrument based on Superconducting Tunneling Junctions (STJs) with μs time resolution and at 2 GHz using the Nançay radio telescope with an instrument doing coherent dedispersion and able to record giant pulses data. Aims: We have studied the delay between the radio and optical pulse using simultaneously obtained data therefore reducing possible uncertainties present in previous observations. Methods: We determined the arrival times of the (mean) optical and radio pulse and compared them using the tempo2 software package. Results: We present the most accurate value for the optical-radio lag of 255 ± 21 μs and suggest the likelihood of a spectral dependence to the excess optical emission asociated with giant radio pulses.

  9. MULTI-WAVELENGTH OBSERVATIONS OF A SAMPLE OF INTERMEDIATE-LUMINOSITY RADIO-LOUD ACTIVE GALAXIES

    International Nuclear Information System (INIS)

    We present the results from exploratory (12-23 ks) XMM-Newton observations of six optically selected, radio-loud active galactic nuclei (AGNs), together with new radio data and a reanalysis of their archival SDSS spectra. The sources were selected in an effort to expand the current sample of radio-loud AGNs suitable for detailed X-ray spectroscopy studies. The sample includes three broad-line and three narrow-line sources, with X-ray luminosities of the order of L2-10keV ∼ 1043 erg s-1. The EPIC spectra of the broad-lined sources can be described by single power laws with photon indices Γ ∼ 1.6 and little to negligible absorption (NH ∼21 cm-2); on the contrary, significant absorption is detected in the narrow-lined objects, NH ∼ 1023 cm-2, one of which displays a prominent (equivalent width ∼2 keV) Fe Kα emission line. Studying their location in several luminosity-luminosity diagrams for radio-loud AGNs, we find that the sources fall at the lower end of the distribution for bright, classical radio-loud AGNs and close to LINER-like sources. As such, and as indicated by the ratios of their optical emission lines, we conclude that the sources of our sample fall on the border between radiatively efficient and inefficient accretion flows. Future deeper studies of these targets at X-rays and longer wavelengths will expand our understanding of the central engines of radio-loud AGNs at a critical transition region.

  10. Modelling the multi-wavelength emission of flat-spectrum radio quasar 3C 279

    Science.gov (United States)

    Zheng, Y. G.; Yang, C. Y.

    2016-04-01

    We employ a length-dependent conical jet model for the jet structure and emission properties of flat-spectrum radio quasar 3C 279 in the steady state. In the model, ultra-relativistic leptons are injected at the base of the jet and propagate along the jet structure. Non-thermal photons are produced by both synchrotron emission and inverse Compton scattering off synchrotron photons and external soft photons at each segment of the jet. We derive the total energy spectra contribution through integrating every segment. We apply the model to the quasi-simultaneous multi-wavelength observed data of two quiescent epochs. Using the observed radio data of the source, we determine the length of the jet L ˜ 100 pc and the magnetic field B0 ˜ 0.1-1 G at the base of the jet. Assuming a steady geometry of the jet structure and suitable physical parameters, we reproduce the multi-wavelength spectra during two quiescent observed epochs. Our results show that the initial γ-ray emission site is ˜0.5 pc from the black hole.

  11. Modelling the multi-wavelength emission of flat spectrum radio quasar 3C 279

    CERN Document Server

    Zheng, Y G

    2016-01-01

    We employ a length-dependent conical jet model for the jet structure and emission properties of flat spectrum radio quasar 3C 279 in the steady state. In the model, ultra-relativistic leptons are injected at the base of jet and propagate along the jet structure, non-thermal photons are produced by both synchrotron emission and inverse Comtpon scattering off synchrotron photons and external soft photons at each segment of jet. We derive the total energy spectra contribution through integrating every segment. We apply the model to the quasi-simultaneous multi-wavelength observed data of two quiescent epoches. Using the observed radio data of source, we determine the length of jet $L\\sim 100$ pc, and magnetic field $B_{0}\\sim 0.1-1$ G at the base of jet. Assuming a steady geometry of the jet structure and suitable physical parameters, we reproduce the multi-wavelength spectra during two quiescent observed epoches, respectively. Our results show that the initial $\\gamma$-ray emission site takes place at $\\sim 0.5...

  12. Surveying the Dynamic Radio Sky with the Long Wavelength Demonstrator Array

    CERN Document Server

    Lazio, T J W; Lane, W M; Gross, C; Kassim, N E; Ray, P S; Wood, D; York, J A; Kerkhoff, A; Hicks, B; Polisensky, E; Stewart, K; Dalal, N Paravastu; Cohen, A S; Erickson, W C

    2010-01-01

    This paper presents a search for radio transients at a frequency of 73.8 MHz (4 m wavelength) using the all-sky imaging capabilities of the Long Wavelength Demonstrator Array (LWDA). The LWDA was a 16-dipole phased array telescope, located on the site of the Very Large Array in New Mexico. The field of view of the individual dipoles was essentially the entire sky, and the number of dipoles was sufficiently small that a simple software correlator could be used to make all-sky images. From 2006 October to 2007 February, we conducted an all-sky transient search program, acquiring a total of 106 hr of data; the time sampling varied, being 5 minutes at the start of the program and improving to 2 minutes by the end of the program. We were able to detect solar flares, and in a special-purpose mode, radio reflections from ionized meteor trails during the 2006 Leonid meteor shower. We detected no transients originating outside of the solar system above a flux density limit of 500 Jy, equivalent to a limit of no more t...

  13. Variability of fluxes extragalactic radio sources 3С120, 3С273, BL Lac, OJ 287 , its "spectrums periods" and VLBI data on the centimeters waves

    Science.gov (United States)

    Donskykh, Ann; Ryabov, Mikhail; Sukharev, Artem

    We analyzed long and short term monitoring of data fluxes of extragalactic sources 3C120, 3C273, BL Lac, OJ 287 obtained at frequencies of 14.5 GHz (1974-2011), 8 GHz (1971-2011), 4.8GHz and (1979-2010), on the RT-26, University of Michigan, USA. Variability of the flux of the radio source was investigated by applying wavelet analysis. There were identified long-period and short components at all studied frequencies and it was determined the time of their existence. The "spectra periods" for each year of observation were built to assess the contribution of individual periods in the formation of the most powerful phase of activity of the radio sources. The dynamics of the manifestations of active periods at different frequencies was observed. The obtained data was compared with the results of MOJAVE VLBI monitoring for the period of 1995-2012 years at a frequency of 15.4 GHz. It allowed to investigate the structure of emissions during periods of manifestation activity maxima.

  14. Space-based aperture array for ultra-long wavelength radio astronomy

    Science.gov (United States)

    Rajan, Raj Thilak; Boonstra, Albert-Jan; Bentum, Mark; Klein-Wolt, Marc; Belien, Frederik; Arts, Michel; Saks, Noah; van der Veen, Alle-Jan

    2016-02-01

    The past decade has seen the advent of various radio astronomy arrays, particularly for low-frequency observations below 100 MHz. These developments have been primarily driven by interesting and fundamental scientific questions, such as studying the dark ages and epoch of re-ionization, by detecting the highly red-shifted 21 cm line emission. However, Earth-based radio astronomy observations at frequencies below 30 MHz are severely restricted due to man-made interference, ionospheric distortion and almost complete non-transparency of the ionosphere below 10 MHz. Therefore, this narrow spectral band remains possibly the last unexplored frequency range in radio astronomy. A straightforward solution to study the universe at these frequencies is to deploy a space-based antenna array far away from Earths' ionosphere. In the past, such space-based radio astronomy studies were principally limited by technology and computing resources, however current processing and communication trends indicate otherwise. Furthermore, successful space-based missions which mapped the sky in this frequency regime, such as the lunar orbiter RAE-2, were restricted by very poor spatial resolution. Recently concluded studies, such as DARIS (Disturbuted Aperture Array for Radio Astronomy In Space) have shown the ready feasibility of a 9 satellite constellation using off the shelf components. The aim of this article is to discuss the current trends and technologies towards the feasibility of a space-based aperture array for astronomical observations in the Ultra-Long Wavelength (ULW) regime of greater than 10 m i.e., below 30 MHz. We briefly present the achievable science cases, and discuss the system design for selected scenarios such as extra-galactic surveys. An extensive discussion is presented on various sub-systems of the potential satellite array, such as radio astronomical antenna design, the on-board signal processing, communication architectures and joint space-time estimation of the

  15. Deep searches for decameter wavelength pulsed emission from radio-quiet gamma-ray pulsars

    CERN Document Server

    Maan, Yogesh

    2014-01-01

    We report the results of (a) extensive follow-up observations of the gamma-ray pulsar J1732-3131 that has been recently detected at decameter wavelengths, and (b) deep searches for counterparts of 9 other radio-quiet gamma-ray pulsars at 34 MHz, using the Gauribidanur radio telescope. No periodic signal from J1732-3131 could be detected above a detection threshold of $8\\sigma$, even with an effective integration time of more than 40 hours. However, the average profile obtained by combining data from several epochs, at a dispersion measure of 15.44 pc/cc, is found to be consistent with that from the earlier detection of this pulsar at a confidence level of 99.2 %. We present this consistency between the two profiles as an evidence that J1732-3131 is a faint radio pulsar with an average flux density of 200--400 mJy at 34 MHz. Detection sensitivity of our deep searches, despite the extremely bright sky background at such low frequencies, is generally comparable to that of higher frequency searches for these puls...

  16. Radio wavelength observations of magnetic fields on active dwarf M, RS CVn and magnetic stars

    Science.gov (United States)

    Lang, Kenneth R.

    1986-01-01

    The dwarf M stars, YZ Canis Minoris and AD Leonis, exhibit narrow-band, slowly varying (hours) microwave emission that cannot be explained by conventional thermal radiation mechanisms. The dwarf M stars, AD Leonis and Wolf 424, emit rapid spikes whose high brightness temperatures similarly require a nonthermal radiation process. They are attributed to coherent mechanisms such as an electron-cyclotron maser or coherent plasma radiation. If the electron-cyclotron maser emits at the second or third harmonic gyrofrequency, the coronal magnetic field strength equals 250 G or 167 G, and constraints on the plasma frequency imply an electron density of 6 x 10 to the 9th/cu cm. Radio spikes from AD Leonis and Wolf 424 have rise times less than or equal to 5 ms, indicating a linear size of less than or equal to 1.5 x 10 to the 8th cm, or less than 0.005 of the stellar radius. Although Ap magnetic stars have strong dipole magnetic fields, they exhibit no detectable gyroresonant radiation, suggesting that these stars do not have hot, dense coronae. The binary RS CVn star UX Arietis exhibits variable emission at 6 cm wavelength on time scales ranging from 30 s to more than one hour.

  17. The Chromospheric Solar Limb Brightening at Radio, Millimeter, Sub-millimeter, and Infrared Wavelengths

    CERN Document Server

    De la Luz, Victor

    2016-01-01

    Observations of the emission at radio, millimeter, sub-millimeter, and infrared wavelengths in the center of the solar disk validate the auto-consistence of semi-empirical models of the chromosphere. Theoretically, these models must reproduce the emission at the solar limb. In this work, we tested both the VALC and the C7 semi-empirical models by computing their emission spectrum in the frequency range from 2 GHz to 10 THz, at solar limb altitudes. We calculate the Sun's theoretical radii as well as their limb brightening. Non-Local Thermodynamic Equilibrium (NLTE) was computed for hydrogen, electron density, and H-. In order to solve the radiative transfer equation a 3D geometry was employed to determine the ray paths and Bremsstrahlung, H-, and inverse Bremsstrahlung opacity sources were integrated in the optical depth. We compared the computed solar radii with high resolution observations at the limb obtained by Clark (1994). We found that there are differences between observed and computed solar radii of ...

  18. Estimation of the Apparent Source Size of Solar Radio Emissions Using SVD: An Application to Type III Radio Bursts at Long Wavelengths Observed by STEREO and Wind

    Czech Academy of Sciences Publication Activity Database

    Krupař, Vratislav; Santolík, Ondřej; Cecconi, B.; Maksimovic, M.

    Prague : MATFYZPRESS, 2010 - (Šafránková, J.; Pavlů, J.), s. 121-127 ISBN 978-80-7378-140-8. [Week of Doctoral Students 2010. Annual Student Conference /19./. Prague (CZ), 01.06.2010-04.06.2010] R&D Projects: GA MŠk ME09107; GA AV ČR IAA301120601 Institutional research plan: CEZ:AV0Z30420517 Keywords : Solar Radio * SVD * Wavelengths * STEREO Subject RIV: BL - Plasma and Gas Discharge Physics

  19. The impact of SZ effect on cm-wavelength (1-30 GHz) observation of galaxy cluster radio relics

    CERN Document Server

    Basu, Kaustuv; Erler, Jens; Sommer, Martin

    2015-01-01

    (Abridged) Radio relics in galaxy clusters are believed to be associated with powerful shock fronts that originate during cluster mergers, and are a testbed for the acceleration of relativistic particles in the intracluster medium. Recently, radio relic observations have pushed into the cm-wavelength domain (1-30 GHz) where a break from the standard synchrotron power-law spectrum has been found, most noticeably in the famous 'Sausage' relic. In this paper, we point to an important effect that has been ignored or considered insignificant while interpreting these new high-frequency radio data, namely the contamination due to the Sunyaev-Zel'dovich (SZ) effect that changes the observed radio flux. Even though the radio relics reside in the cluster outskirts, the shock-driven pressure boost increases the SZ signal locally by roughly an order of magnitude. The resulting flux contamination for some well-known relics are non-negligible already at 10 GHz, and at 30 GHz the observed radio fluxes can be diminished by a...

  20. Small-scale structure of quasars and galactic nuclei at radio wavelengths

    International Nuclear Information System (INIS)

    Recent results from high-resolution radio interferometry of extragalactic sources are described. Reasonable models of compact radio sources are considered. Several sources with regular increases in apparent angular size seem most simply to be explained as relativistic expansion. 22 references

  1. A multi-wavelength investigation of the radio-loud supernova PTF11qcj and its circumstellar environment

    International Nuclear Information System (INIS)

    We present the discovery, classification, and extensive panchromatic (from radio to X-ray) follow-up observations of PTF11qcj, a supernova (SN) discovered by the Palomar Transient Factory (PTF). Our observations with the Karl G. Jansky Very Large Array show that this event is radio-loud: PTF11qcj reached a radio peak luminosity comparable to that of the famous gamma-ray-burst-associated SN 1998bw (L 5 GHz ≈ 1029 erg s–1 Hz–1). PTF11qcj is also detected in X-rays with the Chandra Observatory, and in the infrared band with Spitzer. Our multi-wavelength analysis probes the SN interaction with circumstellar material. The radio observations suggest a progenitor mass-loss rate of ∼10–4 M ☉ yr–1 × (vw /1000 km s–1), and a velocity of ≈0.3-0.5 c for the fastest moving ejecta (at ≈10 days after explosion). However, these estimates are derived assuming the simplest model of SN ejecta interacting with a smooth circumstellar wind, and do not account for possible inhomogeneities in the medium and asphericity of the explosion. The radio data show deviations from such a simple model, as well as a late-time re-brightening. The X-ray flux from PTF11qcj is compatible with the high-frequency extrapolation of the radio synchrotron emission (within the large uncertainties). A light echo from pre-existing dust is in agreement with our infrared data. Our pre-explosion data from the PTF suggest that a precursor eruption of absolute magnitude Mr ≈ –13 mag may have occurred ≈2.5 yr prior to the SN explosion. Overall, PTF11qcj fits the expectations from the explosion of a Wolf-Rayet star. Precursor eruptions may be a feature characterizing the final pre-explosion evolution of such stars.

  2. The Amateur Radio Club: want to be on the same wavelength?

    CERN Multimedia

    2008-01-01

    We all know about cosmic background radiation, but most of us are probably less familiar with other forms of radio signals at CERN. Here’s an opportunity to discover the CERN Amateur Radio Club (CARC) - callsign F6KAR - which is currently installing a new shortwave antenna. Two-way communications between radio stations are followed up with written confirmations, known as QSL cards, bearing the radio operators’ callsigns. The CARC’s collection contains more than 10 000 cards from all over the world. You don’t have to be NASA and have the most advanced technology to be able to contact space! The amateur radio enthusiasts of the CARC ably demonstrated this in 2005, when they succeeded in communicating with the International Space Station (ISS). The link-up was part of a school project in which thirty children came to CERN to find out about amateur radio and were given the opportunity to ask the astronauts a series of questions. ...

  3. Enabled scalable and privacy wavelength division multiplexing-radio over fiber system based on optical virtual private networks

    Science.gov (United States)

    Zhang, Qiaoyan; Zhang, Chongfu; Jin, Wei; Qiu, Kun

    2014-06-01

    A new wavelength division multiplexing (WDM)-based radio over fiber (RoF) system is proposed for optical virtual private network (OVPN) communication between inter-base stations (inter-BSs) or intra-BSs, using four-wave mixing (FWM) in a semiconductor optical amplifier as well as wavelength reflection of fiber Bragg gratings. By establishing inter-BSs and intra-BSs OVPN link of a 60-GHz WDM-RoF system, the private channels for the communication of end users under different BSs of sub-RoFs can be provided. In our scheme, 58 and 60-GHz millimeter waves are used to carry OVPN data and downstream data, respectively. Furthermore, the scalability of the proposed system is improved by the integration of an RoF system, WDM, and FWM. The simulation results successfully verify the feasibility of our proposed scheme.

  4. Space-based Aperture Array For Ultra-Long Wavelength Radio Astronomy

    CERN Document Server

    Rajan, Raj Thilak; Bentum, Mark; Klein-Wolt, Marc; Belien, Frederik; Arts, Michel; Saks, Noah; van der Veen, Alle-Jan

    2015-01-01

    The past decade has seen the rise of various radio astronomy arrays, particularly for low-frequency observations below 100MHz. These developments have been primarily driven by interesting and fundamental scientific questions, such as studying the dark ages and epoch of re-ionization, by detecting the highly red-shifted 21cm line emission. However, Earth-based radio astronomy below frequencies of 30MHz is severely restricted due to man-made interference, ionospheric distortion and almost complete non-transparency of the ionosphere below 10MHz. Therefore, this narrow spectral band remains possibly the last unexplored frequency range in radio astronomy. A straightforward solution to study the universe at these frequencies is to deploy a space-based antenna array far away from Earths' ionosphere. Various studies in the past were principally limited by technology and computing resources, however current processing and communication trends indicate otherwise. We briefly present the achievable science cases, and dis...

  5. Imaging of the Radio Remnant of SN 1987A at 12 mm Wavelength

    OpenAIRE

    Manchester, R. N.; Gaensler, B. M.; Staveley-Smith, L.; Kesteven, M. J.; Tzioumis, A. K.

    2005-01-01

    Observations of the radio remnant of Supernova 1987A using the Australia Telescope Compact Array in the 12-mm band on 2003 July 31 (day 6002.7 after the explosion) give the first fully resolved radio image of the supernova remnant. The diffraction-limited image has a resolution of about 0.45 arcsec, a factor of two better than that of the 3-cm images previously obtained. There is excellent agreement between the 12-mm image and a contemporaneous super-resolved 3-cm image. Super-resolution of t...

  6. The repeating Fast Radio Burst FRB 121102: Multi-wavelength observations and additional bursts

    CERN Document Server

    Scholz, P; Hessels, J W T; Chatterjee, S; Cordes, J M; Kaspi, V M; Wharton, R S; Bassa, C G; Bogdanov, S; Camilo, F; Crawford, F; Deneva, J; van Leeuwen, J; Lynch, R; Madsen, E C; McLaughlin, M A; Mickaliger, M; Parent, E; Patel, C; Ransom, S M; Seymour, A; Stairs, I H; Stappers, B W; Tendulkar, S P

    2016-01-01

    We report on radio and X-ray observations of the only known repeating Fast Radio Burst (FRB) source, FRB 121102. We have detected six additional radio bursts from this source: five with the Green Bank Telescope at 2 GHz, and one at 1.4 GHz at the Arecibo Observatory for a total of 17 bursts from this source. All have dispersion measures consistent with a single value ($\\sim559$ pc cm$^{-3}$) that is three times the predicted maximum Galactic value. The 2-GHz bursts have highly variable spectra like those at 1.4 GHz, indicating that the frequency structure seen across the individual 1.4 and 2-GHz bandpasses is part of a wideband process. X-ray observations of the FRB 121102 field with the Swift and Chandra observatories show at least one possible counterpart; however, the probability of chance superposition is high. A radio imaging observation of the field with the Jansky Very Large Array at 1.6 GHz yields a 5$\\sigma$ upper limit of 0.3 mJy on any point-source continuum emission. This upper limit, combined wit...

  7. Imaging of the Radio Remnant of SN 1987A at 12 mm Wavelength

    CERN Document Server

    Manchester, R N; Staveley-Smith, L; Kesteven, M J; Tzioumis, A K

    2005-01-01

    Observations of the radio remnant of Supernova 1987A using the Australia Telescope Compact Array in the 12-mm band on 2003 July 31 (day 6002.7 after the explosion) give the first fully resolved radio image of the supernova remnant. The diffraction-limited image has a resolution of about 0.45 arcsec, a factor of two better than that of the 3-cm images previously obtained. There is excellent agreement between the 12-mm image and a contemporaneous super-resolved 3-cm image. Super-resolution of the 12-mm image gives a further factor of two improvement in resolution, to 0.25 arcsec, albeit with limited dynamic range. While the spatial distributions of the radio and X-ray emission are broadly similar, there are significant differences in detail with no correspondence in the regions of brightest emission. The 12-mm image is well modelled by a thick equatorial ring inclined at 43 deg to the line of sight. This, together with the common east-west asymmetry and the relatively steady increase in the radio flux density, ...

  8. Observation of a Quasi-periodic Pulsation in Hard X-ray, Radio and Extreme-ultraviolet Wavelengths

    CERN Document Server

    Kumar, Pankaj; Cho, Kyung-Suk

    2016-01-01

    We present multi-wavelength analysis of a quasi-periodic pulsation (QPP) observed in the hard X-ray, radio, and extreme-ultraviolet (EUV) channels during an M1.9 flare occurred on 23-24 September 2011. The non-thermal hard X-ray emission in 25-50 keV observed by RHESSI shows five distinct impulsive peaks of decaying amplitude with a period of about three minutes. Similar QPP was observed in the microwave emission recorded by the Nobeyama Radioheliograph and Polarimeter in the 8.8, 15, 17 GHz channels. Interestingly, the 3-min QPP was also observed in the metric and decimetric radio frequencies (25-180, 245, 610 MHz) as repetitive type III bursts. Multi-wavelength observations from the SDO/AIA, Hinode/SOT, and STEREO/SECCHI suggest a fan-spine topology at the eruption site, associated with the formation of a quasi-circular ribbon during the flare. A small filament was observed below the fan-loops before the flare onset. The filament rose slowly and interacted with the ambient field. This behaviour was followed...

  9. On the Visibility of Prominence Fine Structures at Radio Millimeter Wavelengths

    Czech Academy of Sciences Publication Activity Database

    Heinzel, Petr; Berlicki, Arkadiusz; Bárta, Miroslav; Karlický, Marian; Rudawy, P.

    2015-01-01

    Roč. 290, č. 7 (2015), s. 1981-2000. ISSN 0038-0938 R&D Projects: GA ČR GAP209/12/0906; GA ČR GAP209/12/0103; GA ČR GA13-24782S Institutional support: RVO:67985815 Keywords : prominences * quiescent * radio emission Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.039, year: 2014

  10. A multi-wavelength investigation of the radio-loud supernova PTF11qcj and its circumstellar environment

    Energy Technology Data Exchange (ETDEWEB)

    Corsi, A. [Department of Physics, The George Washington University, 725 21st St, NW, Washington, DC 20052 (United States); Ofek, E. O.; Gal-Yam, A.; Xu, D. [Benoziyo Center for Astrophysics, Weizmann Institute of Science, 76100 Rehovot (Israel); Frail, D. A. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Kulkarni, S. R.; Horesh, A.; Carpenter, J.; Arcavi, I.; Cao, Y.; Mooley, K.; Sesar, B. [Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Fox, D. B. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Kasliwal, M. M. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Sullivan, M.; Maguire, K.; Pan, Y.-C. [Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Cenko, S. B. [NASA Goddard Space Flight Center, Code 685, Greenbelt, MD 20771 (United States); Sternberg, A. [Max-Planck-Institut fur Astrophysik, D-85741 Garching (Germany); Bersier, D., E-mail: corsi@gwu.edu [Astrophysics Research Institute, Liverpool John Moores University, Liverpool (United Kingdom); and others

    2014-02-10

    We present the discovery, classification, and extensive panchromatic (from radio to X-ray) follow-up observations of PTF11qcj, a supernova (SN) discovered by the Palomar Transient Factory (PTF). Our observations with the Karl G. Jansky Very Large Array show that this event is radio-loud: PTF11qcj reached a radio peak luminosity comparable to that of the famous gamma-ray-burst-associated SN 1998bw (L {sub 5} {sub GHz} ≈ 10{sup 29} erg s{sup –1} Hz{sup –1}). PTF11qcj is also detected in X-rays with the Chandra Observatory, and in the infrared band with Spitzer. Our multi-wavelength analysis probes the SN interaction with circumstellar material. The radio observations suggest a progenitor mass-loss rate of ∼10{sup –4} M {sub ☉} yr{sup –1} × (v{sub w} /1000 km s{sup –1}), and a velocity of ≈0.3-0.5 c for the fastest moving ejecta (at ≈10 days after explosion). However, these estimates are derived assuming the simplest model of SN ejecta interacting with a smooth circumstellar wind, and do not account for possible inhomogeneities in the medium and asphericity of the explosion. The radio data show deviations from such a simple model, as well as a late-time re-brightening. The X-ray flux from PTF11qcj is compatible with the high-frequency extrapolation of the radio synchrotron emission (within the large uncertainties). A light echo from pre-existing dust is in agreement with our infrared data. Our pre-explosion data from the PTF suggest that a precursor eruption of absolute magnitude M{sub r} ≈ –13 mag may have occurred ≈2.5 yr prior to the SN explosion. Overall, PTF11qcj fits the expectations from the explosion of a Wolf-Rayet star. Precursor eruptions may be a feature characterizing the final pre-explosion evolution of such stars.

  11. The impact of the SZ effect on cm-wavelength (1-30 GHz) observations of galaxy cluster radio relics

    Science.gov (United States)

    Basu, Kaustuv; Vazza, Franco; Erler, Jens; Sommer, Martin

    2016-07-01

    Radio relics in galaxy clusters are believed to be associated with powerful shock fronts that originate during cluster mergers, and are a testbed for the acceleration of relativistic particles in the intracluster medium. Recently, radio relic observations have pushed into the cm-wavelength domain (1-30 GHz) where a break from the standard synchrotron power law spectrum has been found, most noticeably in the famous "Sausage" relic. Such spectral steepening is seen as an evidence for non-standard relic models, such as ones requiring seed electron population with a break in their energy spectrum. In this paper, however, we point to an important effect that has been ignored or considered insignificant while interpreting these new high-frequency radio data, namely the contamination due to the Sunyaev-Zel'dovich (SZ) effect that changes the observed synchrotron flux. Even though the radio relics reside in the cluster outskirts, the shock-driven pressure boost increases the SZ signal locally by roughly an order of magnitude. The resulting flux contamination for some well-known relics are non-negligible already at 10 GHz, and at 30 GHz the observed synchrotron fluxes can be diminished by a factor of several from their true values. At higher redshift the contamination gets stronger due to the redshift independence of the SZ effect. Interferometric observations are not immune to this contamination, since the change in the SZ signal occurs roughly at the same length scale as the synchrotron emission, although there the flux loss is less severe than single-dish observations. Besides presenting this warning to observers, we suggest that the negative contribution from the SZ effect can be regarded as one of the best evidence for the physical association between radio relics and shock waves. We present a simple analytical approximation for the synchrotron-to-SZ flux ratio, based on a theoretical radio relic model that connects the nonthermal emission to the thermal gas properties

  12. Observation of a Quasiperiodic Pulsation in Hard X-Ray, Radio, and Extreme-ultraviolet Wavelengths

    Science.gov (United States)

    Kumar, Pankaj; Nakariakov, Valery M.; Cho, Kyung-Suk

    2016-05-01

    We present a multiwavelength analysis of a quasiperiodic pulsation (QPP) observed in the hard X-ray (HXR), radio, and extreme-ultraviolet (EUV) channels during an M1.9 flare that occurred on 2011 September 23–24. The nonthermal HXR emission in 25–50 keV observed by RHESSI shows five distinct impulsive peaks of decaying amplitude with a period of about 3 minutes. A similar QPP was observed in the microwave emission recorded by the Nobeyama Radioheliograph and Polarimeter in the 2, 3.75, 9.4, and 17 GHz channels. Interestingly, the 3-minute QPP was also observed in the metric and decimetric radio frequencies (25–180, 245, 610 MHz) as repetitive type III bursts. Multiwavelength observations from the Solar Dynamics Observatory/Atmospheric Image Assembly, Hinode/SOT, and Solar TErrestrial RElations Observatory/SECCHI suggest a fan-spine topology at the eruption site, associated with the formation of a quasi-circular ribbon during the flare. A small filament was observed below the fan loops before the flare onset. The filament rose slowly and interacted with the ambient field. This behavior was followed by an untwisting motion of the filament. Two different structures of the filament showed an approximately 3-minute periodic alternate rotation in the clockwise and counterclockwise directions. The 3-minute QPP was found to highly correlate with 3-minute oscillations in a nearby sunspot. We suggest that the periodic reconnection (modulated either by a sunspot slow-mode wave or by an untwisting filament) at a magnetic null point most likely causes the repetitive particle acceleration, generating the QPP observed in HXR, microwave, and type III radio bursts.

  13. Radio-over-fiber system with tunable millimeter-wave generation and wavelength reuse for uplink connection

    Science.gov (United States)

    Zhang, Chan; Ning, Tigang; Li, Jing; Lin, Heng; Liu, Zhiming

    2016-03-01

    We propose and demonstrate a radio-over-fiber system to generate an optical millimeter wave (MMW) and realize wavelength reuse for an uplink connection. A tunable optical comb generated by a single Fabry-Perot laser serves as the optical source. The central carrier is separated by an optical circulator cascaded with a fiber Bragg grating. For the downlink, the unmodulated central carrier is coupled with one subcarrier, which has been modulated with 2.5-Gb/s data. Then, different MMWs can be generated by choosing different subcarriers. While for the uplink, the same central carrier is reused for an uplink connection with 1.25-Gb/s data. In the scheme, a 60-GHz MMW is obtained and the bidirectional data are simultaneously transmitted over 60-km transmission with <0.5-dB power penalty. This system shows a simple cost-efficient configuration and good performance over long-distance delivery.

  14. Cometary models - excitation of molecules at radio wavelengths and thermodynamics of the coma

    International Nuclear Information System (INIS)

    Models for molecular excitation under physical conditions of cometary atmospheres are obviously a requisite for interpreting radio spectroscopic observations of comets. A review of such models is presented. The prevailing excitation mechanism for the rotational lines of parent molecules is pumping of the fundamental vibrational bands by the solar infrared radiation field, followed by spontaneous decay; the molecular rotational population is then at fluorescence equilibrium. Another competing mechanism in the inner coma is thermal excitation by collisions. Its evaluation needs the knowledge of the coma kinetic temperature law, which up to now can only be achieved by modeling the coma thermodynamics. A review of cometary thermodynamical models is also given here, and the relations between such models and cometary molecular observations are discussed. 50 references

  15. Instantaneous Radio Spectra of Giant Pulses from the Crab Pulsar from Decimeter to Decameter Wavelengths

    CERN Document Server

    Popov, M V; Ul'yanov, O M; Deshpande, A A; Ershov, A A; Zakharenko, V V; Kondratiev, V I; Kostyuk, S V; Losovskii, B Y; Soglasnov, V A

    2006-01-01

    The results of simultaneous multifrequency observations of giant radio pulses from the Crab pulsar, PSR B0531+21, at 23, 111, and 600 MHz are presented and analyzed. Giant pulses were detected at a frequency as low as 23 MHz for the first time. Of the 45 giant pulses detected at 23 MHz, 12 were identified with counterparts observed simultaneously at 600 MHz. Of the 128 giant pulses detected at 111 MHz, 21 were identified with counterparts observed simultaneously at 600 MHz. The spectral indices for the power-law frequency dependence of the giant-pulse energies are from -3.1 to -1.6. The mean spectral index is -2.7 +/- 0.1 and is the same for both frequency combinations (600-111 MHz and 600-23 MHz). The large scatter in the spectral indices of the individual pulses and the large number of unidentified giant pulses suggest that the spectra of the individual giant pulses do not actually follow a simple power law. The observed shapes of the giant pulses at all three frequencies are determined by scattering on int...

  16. Dense wavelength division multiplexing photonic transport for radio frequency and microwave wireless services

    Science.gov (United States)

    Paolella, Arthur C.; Jemison, William D.; Borlando, Javier; Wang, Jun

    2004-10-01

    The expected increase in space and terrestrial services that include two-way fixed, SATCOM, CATV and mobile wireless services require expanding the system capacity. This expansion has created an opportunity for the utilization of the demonstrated photonic transport systems in wireless networks. System demonstrations and architectural developments have been proposed for distribution of communication services over fiber. Termed Fiber Radio and Hybrid Fiber Wireless, these systems offer the potential to improve services and reduce base station costs through increased bandwidth and ease of installation. We have developed and demonstrated DWDM broadband photonic transport systems able to meet the requirements for IS-95 Personal Communications Services operating at 1.9 GHz and Broadband Wireless Internet operating over the band of 2.5 to 2.7 GHz. Each DWDM channel operates from 1 to 3 GHz transporting services up to 80 Km. Solutions are being sought for low cost transmitters to meet DWDM SATCOM system requirements include extending the transmission distance to over 100 Km with a bandwidth that exceeds multiple octaves. These new requirements put high performance demands on the optical components. We have developed high performance transmitters based on electro-absorption modulated lasers (EML) that can meet SATCOM requirements. We have shown that the EML is capable of providing the required CNR of 32 dB for satellite transmission in the band of 950 to 2150 MHz over a 100 Km distance. In addition, we are investigating a new modulation technique, Microwave Photonic Vector Modulation (MPVM), which has the potential for wideband transmission in DWDM systems.

  17. The Radio Wavelength Time Delay of Gravitational Lens 0957+561

    CERN Document Server

    Haarsma, D B; Lehár, J; Burke, Bernard F; Haarsma, Deborah B.; Hewitt, Jacqueline N.; Lehár, Joseph; Burke, Bernard F.

    1999-01-01

    The gravitational lens 0957+561 was monitored with the Very Large Array from 1979 to 1997. The 6 cm light curve data from 1995-1997 and the 4 cm data from 1990-1997 are reported here. At 4 cm, the intrinsic source variations occur earlier and are twice as large as the corresponding variations at 6 cm. The VLBI core and jet components have different magnification factors, leading to different flux ratios for the varying and non-varying portions of the VLA light curves. Using both the PRHQ and Dispersion statistical techniques, we determined the time delay, core flux ratio, and excess non-varying B image flux density. The fits were performed for the 4 cm and 6 cm light curves, both individually and jointly, and we used Gaussian Monte Carlo data to estimate 68% statistical confidence levels. The delay estimates from each individual wavelength were inconsistent given the formal uncertainties, suggesting that there are unmodeled systematic errors in the analysis. We roughly estimate the systematic uncertainty in t...

  18. Signatures of stellar mass ejections at radio and FUV wavelengths - implications for planetary mass loss

    International Nuclear Information System (INIS)

    Highly energetic activity phenomena such as flares and Coronal Mass Ejections (CMEs) lead to thermal and non-thermal planetary atmospheric mass loss. Knowledge of stellar CME parameters is poor, therefore the aim of the first part of the thesis is the detection of signatures of stellar CMEs from which parameters can be derived, which can then be used to model non-thermal planetary atmospheric mass loss. Two different approaches have been established. For approach 1 the correlation of decameter type II radio bursts and CMEs on the Sun was extrapolated to stars. Ten nights of observations from the UTR-2 decameter array of the dMe star AD Leo were analysed and a handful of possible stellar type III-like bursts were detected, but no type II-like bursts. For approach 2 the Doppler shift of spectral lines was used as a signature of stellar CMEs. Several hours of far ultraviolet data of the active stars AD Leo, AU Mic, and AB Dor were searched for such signatures. Only AD Leo revealed one spectral line asymmetry in the blue wing of the first component of the OVI duplet at 1032 A shifted by -84 km/s two hours after a flare. In addition the electron density-sensitive line ratio CIII(1176 A)/CIII(977 A) was investigated and found to be enhanced during stellar flaring. This finding was also investigated on the Sun where a similar behaviour for powerful solar flares was found. Due to a lack of coinciding data a correlation of the carbon ion line ratio and CMEs could not be investigated. In the second part of the thesis the thermal planetary atmospheric mass loss was investigated theoretically and found to be most efficient for close-in low density planets. By using a modified energy-limited approach the thermal mass loss of the recently discovered Super-earths CoRoT-7b and Kepler-10b was calculated and found to be in the order of one earth mass. Therefore it is concluded that both planets cannot be the remnants of Jupiter- or Saturn-sized gas giants. (author)

  19. The Crab Pulsar at Centimeter Wavelengths II: Single Pulses

    CERN Document Server

    Hankins, T H; Jones, G

    2016-01-01

    We have carried out new, high-frequency, high-time-resolution observations of the Crab pulsar. Combining these with our previous data, we characterize bright single pulses associated with the Main Pulse, both the Low-Frequency and High-Frequency Interpulses, and the two High-Frequency Components. Our data include observations at frequencies ranging from 1 to 43 GHz with time resolution down to a fraction of a nanosecond. We find at least two types of emission physics are operating in this pulsar. Both Main Pulses and Low-Frequency Interpulses, up to about 10 GHz, are characterized by nanoshot emission - overlapping clumps of narrow-band nanoshots, each with its own polarization signature. High-Frequency Interpulses, between 5 and 30 GHz, are characterized by spectral band emission - linearly polarized emission containing about 30 proportionately spaced spectral bands. We cannot say whether the longer-duration High-Frequency Component pulses are due to a scattering process, or if they come from yet another typ...

  20. Radio astronomy ultra-low-noise amplifier for operation at 91 cm wavelength in high RFI environment

    Science.gov (United States)

    Korolev, A. M.; Zakharenko, V. V.; Ulyanov, O. M.

    2016-02-01

    An ultra-low-noise input amplifier intended for a use in a radio telescope operating at 91 cm wavelength is presented. The amplifier noise temperatures are 12.8 ± 1.5 and 10.0 ± 1.5 K at ambient temperatures of 293 and 263 K respectively. The amplifier does not require cryogenic cooling. It can be quickly put in operation thus shortening losses in the telescope observation time. High linearity of the amplifier (output power at 1 dB gain compression P1dB ≥ 22 dBm, output third order intercept point OIP3 ≥ 37 dBm) enables the telescope operation in highly urbanized and industrialized regions. To obtain low noise characteristics along with high linearity, high-electron-mobility field-effect transistors were used in parallel in the circuit developed. The transistors used in the amplifier are cost-effective and commercially available. The circuit solution is recommended for similar devices working in ultra-high frequency band.

  1. The 21 centimeter emission from the reionization epoch: extended and point source foregrounds

    OpenAIRE

    Di Matteo, Tiziana; Ciardi, Benedetta; Miniati, Francesco

    2004-01-01

    Fluctuations in the redshifted 21 centimeter emission from neutral hydrogen probe the epoch of reionization. We examine the observability of this signal and the impact of extragalactic foreground radio sources. We use cosmological simulations to predict the angular correlation functions of intensity fluctuations due to unresolved radio galaxies, cluster radio halos and relics and free-free emission from the interstellar and intergalactic medium at the frequencies and angular scales relevant f...

  2. Centimeter searches for molecular line emission from high-redshift galaxies

    CERN Document Server

    Carilli, C L

    2002-01-01

    We consider the capabilities for detecting low order CO emission lines from high-z galaxies using the next generation of radio telescopes operating at 22 and 43 GHz. We employ models for the evolution of dusty star forming galaxies based on source counts at (sub)millimeter wavelengths, and on the observed mm through infrared backgrounds, to predict the expected detection rate of low-order CO(2-1) and CO(1-0) line emitting galaxies for optimal centimeter(cm)-wave surveys using future radio telescopes, such as the Square Kilometer Array (SKA) and the Expanded Very Large Array (EVLA). We then compare these results to surveys that can be done with the next-generation mm-wave telescope, the Atacama Large Millimeter Array (ALMA). Operating at 22 GHz the SKA will be competitive with the ALMA in terms of the detection rate of lines from high-z galaxies, and will be potentially superior by an order of magnitude if extended to 43 GHz. Perhaps more importantly, cm-wave telescopes are sensitive to lower excitation gas in...

  3. Observation of solar radio bursts of type II and III at kilometer wavelengths from Prognoz-8 during STIP Interval XII

    International Nuclear Information System (INIS)

    Type II and type III radio events were observed at low frequencies (2.16 MHz to 114 kHz) by the Prognoz-8 satellite during the period of STIP Interval XII in April and May, 1981, respectively. This review covers briefly a chronology of the sub-megahertz radio events, and where possible their association with both groundbased radio observations and solar flare. (author)

  4. Statistical Survey of Type III Radio Bursts at Long Wavelengths Observed by the Solar TErrestrial RElations Observatory (STEREO)/Waves Instruments: Goniopolarimetric Properties and Radio Source Locations

    CERN Document Server

    Krupar, Vratislav; Santolik, Ondrej; Cecconi, Baptiste; Kruparova, Oksana

    2014-01-01

    We have performed statistical analysis of a large number of Type III radio bursts observed by STEREO between May 2007 and February 2013. Only intense, simple, and isolated cases have been included in our data set. We have focused on the goniopolarimetric (GP, also referred to as direction-finding) properties at frequencies between $125$ kHz and $2$ MHz. The apparent source size $\\gamma$ is very extended ($\\approx60^\\circ$) for the lowest analyzed frequencies. Observed apparent source sizes $\\gamma$ expand linearly with a radial distance from the Sun at frequencies below $1$ MHz. We have shown that Type III radio bursts statistically propagate in the ecliptic plane. Calculated positions of radio sources suggest that scattering of the primary beam pattern plays an important role in the propagation of Type III radio bursts in the IP medium.

  5. Radio physics of the sun; Proceedings of the Symposium, University of Maryland, College Park, Md., August 7-10, 1979

    Science.gov (United States)

    Kundu, M. R. (Editor); Gergely, T. E.

    1980-01-01

    Papers are presented in the areas of the radio characteristics of the quiet sun and active regions, the centimeter, meter and decameter wavelength characteristics of solar bursts, space observations of low-frequency bursts, theoretical interpretations of solar active regions and bursts, joint radio, visual and X-ray observations of active regions and bursts, and the similarities of stellar radio characteristics to solar radio phenomena. Specific topics include the centimeter and millimeter wave characteristics of the quiet sun, radio fluctuations arising upon the transit of shock waves through the transition region, microwave, EUV and X-ray observations of active region loops and filaments, interferometric observations of 35-GHz radio bursts, emission mechanisms for radio bursts, the spatial structure of microwave bursts, observations of type III bursts, the statistics of type I bursts, and the numerical simulation of type III bursts. Attention is also given to the theory of type IV decimeter bursts, Voyager observations of type II and III bursts at kilometric wavelengths, radio and whitelight observations of coronal transients, and the possibility of obtaining radio observations of current sheets on the sun.

  6. Multi-wavelength Observations of the Radio Magnetar PSR J1622-4950 and Discovery of its Possibly Associated Supernova Remnant

    OpenAIRE

    Anderson, Gemma E.; Gaensler, B. M.; Slane, Patrick Olson; Rea, Nanda; Kaplan, David L.; Posselt, Bettina; Levin, Lina; Johnston, Simon; Murray, Stephen S.; Brogan, Crystal L.; Bailes, Matthew; Bates, Samuel; Benjamin, Robert A.; Ramesh Bhat, N. D.; Burgay, Marta

    2012-01-01

    We present multi-wavelength observations of the radio magnetar PSR J1622-4950 and its environment. Observations of PSR J1622-4950 with Chandra (in 2007 and 2009) and XMM (in 2011) show that the X-ray flux of PSR J1622-4950 has decreased by a factor of ~50 over 3.7 years, decaying exponentially with a characteristic time of 360 +/- 11 days. This behavior identifies PSR J1622-4950 as a possible addition to the small class of transient magnetars. The X-ray decay likely indicates that PSR J1622-4...

  7. Experimental investigation of the angular structure of the quasar 3C196 radio emission in the decameter wavelengths

    International Nuclear Information System (INIS)

    The angular structure of the radio emission from 3C196 is measured at 25, 20 and 16.7 MHz by URAN-1 and URAN-4 radiointerferometers. As it has been found of the two compact details observable at higher frequencies only one remains in the decameter band. The preferrable simple model of the radio brightness, distribution has been suggested for the source. It consists of the observable compact detail and the extended component that has been detected at these frequencies. The component brings about a noticeable increase in the angular size of the object

  8. Infrared-faint radio sources remain undetected at far-infrared wavelengths. Deep photometric observations using the Herschel Space Observatory

    CERN Document Server

    Herzog, Andreas; Middelberg, Enno; Spitler, Lee R; Leipski, Christian; Parker, Quentin A

    2015-01-01

    Showing 1.4 GHz flux densities in the range of a few to a few tens of mJy, infrared-faint radio sources (IFRS) are a type of galaxy characterised by faint or absent near-infrared counterparts and consequently extreme radio-to-infrared flux density ratios up to several thousand. Recent studies showed that IFRS are radio-loud active galactic nuclei (AGNs) at redshifts >=2. This work explores the far-infrared emission of IFRS, providing crucial information on the star forming and AGN activity of IFRS and on the potential link between IFRS and high-redshift radio galaxies (HzRGs). A sample of six IFRS was observed with the Herschel Space Observatory between 100 um and 500 um. Using these results, we constrained the nature of IFRS by modelling their broad-band spectral energy distribution (SED). Furthermore, we set an upper limit on their infrared SED and decomposed their emission into contributions from an AGN and from star forming activity. All six observed IFRS were undetected in all five Herschel far-infrared ...

  9. Statistical survey of type III radio bursts at long wavelengths observed by the Solar TErrestrial RElations Observatory (STEREO)/Waves instruments: radio flux density variations with frequency

    Czech Academy of Sciences Publication Activity Database

    Krupař, Vratislav; Maksimovic, M.; Santolík, Ondřej; Kontar, E. P.; Cecconi, B.; Hoang, S.; Krupařová, Oksana; Souček, Jan; Reid, H.; Zaslavsky, A.

    2014-01-01

    Roč. 289, č. 8 (2014), s. 3121-3135. ISSN 0038-0938 R&D Projects: GA ČR(CZ) GAP209/12/2394; GA ČR GP13-37174P; GA ČR GAP205/10/2279 Institutional support: RVO:68378289 Keywords : solar radio emissions * plasma radiation Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.039, year: 2014 http://link.springer.com/article/10.1007%2Fs11207-014-0522-x

  10. Infrared-faint radio sources remain undetected at far-infrared wavelengths. Deep photometric observations using the Herschel Space Observatory

    Science.gov (United States)

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

    2015-08-01

    Context. Showing 1.4 GHz flux densities in the range of a few to a few tens of mJy, infrared-faint radio sources (IFRS) are a type of galaxy characterised by faint or absent near-infrared counterparts and consequently extreme radio-to-infrared flux density ratios up to several thousand. Recent studies showed that IFRS are radio-loud active galactic nuclei (AGNs) at redshifts ≳2, potentially linked to high-redshift radio galaxies (HzRGs). Aims: This work explores the far-infrared emission of IFRS, providing crucial information on the star forming and AGN activity of IFRS. Furthermore, the data enable examining the putative relationship between IFRS and HzRGs and testing whether IFRS are more distant or fainter siblings of these massive galaxies. Methods: A sample of six IFRS was observed with the Herschel Space Observatory between 100 μm and 500 μm. Using these results, we constrained the nature of IFRS by modelling their broad-band spectral energy distribution (SED). Furthermore, we set an upper limit on their infrared SED and decomposed their emission into contributions from an AGN and from star forming activity. Results: All six observed IFRS were undetected in all five Herschel far-infrared channels (stacking limits: σ = 0.74 mJy at 100 μm, σ = 3.45 mJy at 500 μm). Based on our SED modelling, we ruled out the following objects to explain the photometric characteristics of IFRS: (a) known radio-loud quasars and compact steep-spectrum sources at any redshift; (b) starburst galaxies with and without an AGN and Seyfert galaxies at any redshift, even if the templates were modified; and (c) known HzRGs at z ≲ 10.5. We find that the IFRS analysed in this work can only be explained by objects that fulfil the selection criteria of HzRGs. More precisely, IFRS could be (a) known HzRGs at very high redshifts (z ≳ 10.5); (b) low-luminosity siblings of HzRGs with additional dust obscuration at lower redshifts; (c) scaled or unscaled versions of Cygnus A at any

  11. 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.

  12. Type IIP Supernova SN 2004et: A Multi-Wavelength Study in X-Ray, Optical and Radio

    CERN Document Server

    Misra, Kuntal; Chandra, Poonam; Bhattacharya, D; Ray, Alak K; Sagar, Ram; Lewin, Walter H G

    2007-01-01

    We present X-ray, broad band optical and low frequency radio observations of the bright type IIP supernova SN 2004et. The \\cxo observed the supernova at three epochs, and the optical coverage spans a period of $\\sim$ 470 days since explosion. The X-ray emission softens with time, and we characterise the X-ray luminosity evolution as $\\Lx \\propto t^{-0.4}$. We use the observed X-ray luminosity to estimate a mass-loss rate for the progenitor star of $\\sim \\ee{2}{-6} M_\\odot \\mathrm{yr}^{-1}$. The optical light curve shows a pronounced plateau lasting for about 110 days. Temporal evolution of photospheric radius and color temperature during the plateau phase is determined by making black body fits. We estimate the ejected mass of $^{56}$Ni to be 0.06 $\\pm$ 0.03 M$_\\odot$. Using the expressions of Litvinova & Nad\\"{e}zhin (1985) we estimate an explosion energy of (0.98 $\\pm$ 0.25) $\\times 10^{51}$ erg. We also present a single epoch radio observation of SN 2004et. We compare this with the predictions of the m...

  13. Workshop on Satellite Power Systems (SPS) effects on optical and radio astronomy

    Energy Technology Data Exchange (ETDEWEB)

    Stokes, G.M.; Ekstrom, P.A. (eds.)

    1980-04-01

    The impacts of the SPS on astronomy were concluded to be: increased sky brightness, reducing the effective aperture of terrestrial telescopes; microwave leakage radiation causing erroneous radioastronomical signals; direct overload of radioastronomical receivers at centimeter wavelengths; and unintentional radio emissions associated with massive amounts of microwave power or with the presence of large, warm structures in orbit causing the satellites to appear as individual stationary radio sources; finally, the fixed location of the geostationary satellite orbits would result in fixed regions of the sky being unusable for observations. (GHT)

  14. Workshop on Satellite Power Systems (SPS) effects on optical and radio astronomy

    International Nuclear Information System (INIS)

    The impacts of the SPS on astronomy were concluded to be: increased sky brightness, reducing the effective aperture of terrestrial telescopes; microwave leakage radiation causing erroneous radioastronomical signals; direct overload of radioastronomical receivers at centimeter wavelengths; and unintentional radio emissions associated with massive amounts of microwave power or with the presence of large, warm structures in orbit causing the satellites to appear as individual stationary radio sources; finally, the fixed location of the geostationary satellite orbits would result in fixed regions of the sky being unusable for observations

  15. Radio flares from gamma-ray bursts

    CERN Document Server

    Kopac, D; Kobayashi, S; Virgili, F J; Harrison, R; Japelj, J; Guidorzi, C; Melandri, A; Gomboc, A

    2015-01-01

    We present predictions of centimeter and millimeter radio emission from reverse shocks in the early afterglows of gamma-ray bursts with the goal of determining their detectability with current and future radio facilities. Using a range of GRB properties, such as peak optical brightness and time, isotropic equivalent gamma-ray energy and redshift, we simulate radio light curves in a framework generalized for any circumburst medium structure and including a parametrization of the shell thickness regime that is more realistic than the simple assumption of thick- or thin-shell approximations. Building on earlier work by Mundell et al. (2007) and Melandri et al. (2010) in which the typical frequency of the reverse shock was suggested to lie at radio, rather than optical wavelengths at early times, we show that the brightest and most distinct reverse-shock radio signatures are detectable up to 0.1 -- 1 day after the burst, emphasizing the need for rapid radio follow-up. Detection is easier for bursts with later opt...

  16. Task six report: Spacecraft communication terminal evaluation. [analysis of space communication at six different wavelengths in radio and optical frequency regions

    Science.gov (United States)

    1973-01-01

    An analytical comparison is made of space communication accomplished at six different wavelengths. In the radio band, 2.25, 7.5, and 14.5 GHz systems are analyzed, while at optical wavelengths, 0.53, 1.06 and 10.6 micron systems are examined. The purpose of the comparison is to determine which of these systems will require the least hardware weight to perform a given communication task. The problem is solved by requiring each communication system to meet a given performance while selecting combinations of transmitted power and antenna diameter to obtain the least overall system weight. This performance is provided while maintaining practical values for parameters other than antenna diameter and power, which also affect system performance. The results of the analysis indicate that for future data links over ranges of 42,000 to 84,000 km and with data bandwidths of 100 to 1000 MHz, the CO2 laser system will provide the required performance with the least total system weight impact on a spacecraft.

  17. Correlated Radio-Optical Variations on Intraday Timescales

    Institute of Scientific and Technical Information of China (English)

    Shan-Jie Qian

    2008-01-01

    Correlated radio-optical variations on intraday timescales have been observed (e.g. In BLO 0716+714) and such radio intraday variability is suggested to have an intrinsic ori- gin. Recently, multi-wavelength observations, simultaneous at radio, mm-submm, optical and hard X-rays, of 0716+714, show that during a period of intraday/interday variations at ra- dio and mm wavelengths, the apparent brightness temperature of the source exceeded the Compton-limit (~1012 K) by 2--4 orders of magnitude, but no Compton catastrophe (or no high luminosity of inverse-Compton radiation) was detected. It is also found that the intra- day/interday variations at mm-submm wavelengths are consistent with the evolutionary be- havior of a standard synchrotron source and for the intraday/interday variations at centimeter wavelengths opacity effects can play a significant role, which is consistent with the interpreta- tion suggested previously by Qian et al. Thus the apparent high brightness temperatures may probably be explained in terms of Doppler boosting effects due to bulk relativistic motion of the source. We will argue a scenario to simulate the correlations between the radio and optical variations on intraday timescales observed in BLO 0716+714 in terms of a relativistic shock propagating through a jet with a dual structure.

  18. The 21 centimeter emission from the reionization epoch: extended and point source foregrounds

    CERN Document Server

    Matteo, T D; Miniati, F; Matteo, Tiziana Di; Ciardi, Benedetta; Miniati, Francesco

    2004-01-01

    Fluctuations in the redshifted 21 centimeter emission from neutral hydrogen probe the epoch of reionization. We examine the observability of this signal and the impact of extragalactic foreground radio sources. We use cosmological simulations to predict the angular correlation functions of intensity fluctuations due to unresolved radio galaxies, cluster radio halos and relics and free-free emission from the interstellar and intergalactic medium at the frequencies and angular scales relevant for the proposed 21cm tomography. In accord with previous findings, the brightness temperature fluctuations due to foreground sources are much larger than those from the primary 21cm signal at all scales. In particular, diffuse cluster radio emission, which has been previously neglected, provides the most significant foreground contamination. However, we show that the contribution to the angular fluctuations at scales \\theta > 1' is dominated by the spatial clustering of bright foreground sources. This excess can be remove...

  19. ALMA Science Verification Data: Millimeter Continuum Polarimetry of the Bright Radio Quasar 3C 286

    CERN Document Server

    Nagai, H; Paladino, R; Hull, C L H; Cortes, P; Moellenbrock, G; Fomalont, E; Asada, K; Hada, K

    2016-01-01

    We present full-polarization observations of the compact, steep-spectrum radio quasar 3C~286 made with the ALMA at 1.3~mm. These are the first full-polarization ALMA observations, which were obtained in the framework of Science Verification. A bright core and a south-west component are detected in the total intensity image, similar to previous centimeter images. Polarized emission is also detected toward both components. The fractional polarization of the core is about 17\\%, this is higher than the fractional polarization at centimeter wavelengths, suggesting that the magnetic field is even more ordered in the millimeter radio core than it is further downstream in the jet. The observed polarization position angle (or EVPA) in the core is $\\sim$\\,$39^{\\circ}$, which confirms the trend that the EVPA slowly increases from centimeter to millimeter wavelengths. With the aid of multi-frequency VLBI observations, we argue that this EVPA change is associated with the frequency-dependent core position. We also report ...

  20. ALMA Science Verification Data: Millimeter Continuum Polarimetry of the Bright Radio Quasar 3C 286

    Science.gov (United States)

    Nagai, H.; Nakanishi, K.; Paladino, R.; Hull, C. L. H.; Cortes, P.; Moellenbrock, G.; Fomalont, E.; Asada, K.; Hada, K.

    2016-06-01

    We present full-polarization observations of the compact, steep-spectrum radio quasar 3C 286 made with the Atacama Large Millimeter and Submillimeter Array (ALMA) at 1.3 mm. These are the first full-polarization ALMA observations, which were obtained in the framework of Science Verification. A bright core and a south–west component are detected in the total intensity image, similar to previous centimeter images. Polarized emission is also detected toward both components. The fractional polarization of the core is about 17%; this is higher than the fractional polarization at centimeter wavelengths, suggesting that the magnetic field is even more ordered in the millimeter radio core than it is further downstream in the jet. The observed polarization position angle (or electric vector position angle (EVPA)) in the core is ˜39◦, which confirms the trend that the EVPA slowly increases from centimeter to millimeter wavelengths. With the aid of multi-frequency VLBI observations, we argue that this EVPA change is associated with the frequency-dependent core position. We also report a serendipitous detection of a sub-mJy source in the field of view, which is likely to be a submillimeter galaxy.

  1. Twenty-one centimeter tomography with foregrounds

    CERN Document Server

    Wang, X; Santos, M; Knox, L; Wang, Xiaomin; Tegmark, Max; Santos, Mario; Knox, Lloyd

    2005-01-01

    Twenty-one centimeter tomography is emerging as a powerful tool to explore the end of the cosmic dark ages and the reionization epoch, but it will only be as good as our ability to accurately model and remove astrophysical foreground contamination. Previous treatments of this problem have focused on the angular structure of the signal and foregrounds and what can be achieved with limited spectral resolution (bandwidths in the 1 MHz range). In this paper we introduce and evaluate a ``blind'' method to extract the multifrequency 21cm signal by taking advantage of the smooth frequency structure of the Galactic and extragalactic foregrounds. We find that 21 cm tomography is typically limited by foregrounds on scales $k\\ll 1h/$Mpc and limited by noise on scales $k\\gg 1h/$Mpc, provided that the experimental bandwidth can be made substantially smaller than 0.1 MHz. Our results show that this approach is quite promising even for scenarios with rather extreme contamination from point sources and diffuse Galactic emiss...

  2. Estimation of the density of Martian soil from radiophysical measurements in the 3-centimeter range

    Science.gov (United States)

    Krupenio, N. N.

    1977-01-01

    The density of the Martian soil is evaluated at a depth up to one meter using the results of radar measurement at lambda sub 0 = 3.8 cm and polarized radio astronomical measurement at lambda sub 0 = 3.4 cm conducted onboard the automatic interplanetary stations Mars 3 and Mars 5. The average value of the soil density according to all measurements is rho bar = 1.37 plus or minus 0.33 g/ cu cm. A map of the distribution of the permittivity and soil density is derived, which was drawn up according to radiophysical data in the 3 centimeter range.

  3. Radio Observations of Infrared Luminous High Redshift QSOs

    CERN Document Server

    Carilli, C L; Omont, A; Cox, P; McMahon, R G; Isaak, K G

    2001-01-01

    We present Very Large Array (VLA) observations at 1.4 GHz and 5 GHz of a sample of 12 Quasi-stellar Objects (QSOs) at z = 3.99 to 4.46. The sources were selected as the brightest sources at 250 GHz from the recent survey of Omont et al. (2001). We detect seven sources at 1.4 GHz with flux densities, S_{1.4} > 50 microJy. These centimeter (cm) wavelength observations imply that the millimeter (mm) emission is most likely thermal dust emission. The radio-through-optical spectral energy distributions for these sources are within the broad range defined by lower redshift, lower optical luminosity QSOs. For two sources the radio continuum luminosities and morphologies indicate steep spectrum, radio loud emission from a jet-driven radio source. For the remaining 10 sources the 1.4 GHz flux densities, or limits, are consistent with those expected for active star forming galaxies. If the radio emission is powered by star formation in these systems, then the implied star formation rates are of order 1e3 M_solar/year. ...

  4. Synergetic use of millimeter and centimeter wavelength radars for retrievals of cloud and rainfall parameters

    Directory of Open Access Journals (Sweden)

    S. Y. Matrosov

    2010-01-01

    Full Text Available A remote sensing approach for simultaneous retrievals of cloud and rainfall parameters in the vertical column above the US Department of Energy's (DOE Climate Research Facility at the Tropical Western Pacific (TWP Darwin site in Australia is described. This approach uses vertically pointing measurements from a DOE Ka-band radar and scanning measurements from a nearby C-band radar pointing toward the TWP Darwin site. Rainfall retrieval constraints are provided by data from a surface impact disdrometer. The approach is applicable to stratiform precipitating cloud systems when a separation between the liquid hydrometeor layer, which contains rainfall and liquid water clouds, and the ice hydrometeor layer is provided by the radar bright band. Absolute C-band reflectivities and Ka-band vertical reflectivity gradients in the liquid layer are used for retrievals of the mean layer rain rate and cloud liquid water path (CLWP. C-band radar reflectivities are also used to estimate ice water path (IWP in regions above the melting layer. The retrieval uncertainties of CLWP and IWP for typical stratiform precipitation systems are about 500–800 g m−2 (for CLWP and a factor of 2 (for IWP. The CLWP retrieval uncertainties increase with rain rate, so retrievals for higher rain rates may be impractical. The expected uncertainties of layer mean rain rate retrievals are around 20%, which, in part, is due to constraints available from the disdrometer data. The applicability of the suggested approach is illustrated for two characteristic events observed at the TWP Darwin site during the wet season of 2007. A future deployment of W-band radars at the DOE tropical Climate Research Facilities can improve CLWP estimate accuracies and provide retrievals for a wider range of stratiform precipitating cloud events.

  5. From Centimeter to Millimeter Wavelengths: A High Angular Resolution Study of 3C273

    OpenAIRE

    Krichbaum, T. P.; Witzel, A.; Zensus, J. A.

    2001-01-01

    Comment: 6 pages, 8 figures, appeared in: Proceedings of the 5th European VLBI Network Symposium held at Onsala Space Observatory, June 29-July 1, 2000, eds. J.E. Conway, A.G. Polatidis, R.S. Booth, and Y.M. Pihlstrom, p. 25-30. (ISBN 91-631-0548-9)

  6. A new three-stage evolution model for millimeter to centimeter wavelength outbursts in BL Lacertae

    International Nuclear Information System (INIS)

    The multi-frequency light curves of BL Lacertae during 1997.5-1999.5 have been modeled by four outbursts, each having a 3-stage evolution in the (Sm, vm) plane with distinct rising-plateau-decaying phases. It is shown that the observed light curves can be well fitted for the eight frequencies from 350 GHz to 4.8 GHz. The main characteristics of the model-fitting are: (1) the outbursts are found to have very flat spectra with an optically thin spectral index α (defined as Sv ∝ v-α) of about 0.15. This is consistent with the results previously obtained by Valtaoja et al. (1992); (2) it is found that there is no spectral flattening between the rising-plateau phase and the decay phase. In other words, the optically thin spectral index does not change from the rising-plateau phase to the decay phase. These features are in contrast to the 3-stage shocked-in-jet model proposed by Marscher and Gear (1985) for submm-IR-optical flares, in which a spectral flattening of Δα = 0.5 is predicted when a transition occurs from the Compton/synchrotron phase (or rising-plateau phase) to the adiabatic phase (or decay phase) with α ∼> 0.5 for the shock being non-radiative. We propose a new model to interpret the fitting results, suggesting that the 3-stage evolution of the mm-cm outbursts in BL Lacertae may be related to the process of shock formation and propagation in a highly collimated jet (for example, a 'parabolic' jet). In particular, during the rising phase, the thickness of the synchrotron-radiating region created by the shock may rapidly increase with time (relative to the jet width) due to the rapid injection of relativistic electrons and a magnetic field, and this leads to the observed behavior that the turnover flux density Sm rapidly increases while the turnover frequency vm decreases. In the decay phase, the emitting plasma enters into a free expansion regime without further injection of relativistic electrons and a magnetic field (for example, when a transition from a collimated regime into a conical regime occurs). The plateau phase is a short period between the two regimes with no distinct features determined.

  7. Design and Calibration of a Cryogenic Blackbody Calibrator at Centimeter Wavelengths

    CERN Document Server

    Kogut, A J; Fixsen, D J; Limon, M; Mirel, P G A; Levin, S; Seiffert, M; Lubin, P M

    2004-01-01

    We describe the design and calibration of an external cryogenic blackbody calibrator used for the first two flights of the Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE) instrument. The calibrator consists of a microwave absorber weakly coupled to a superfluid liquid helium bath. Half-wave corrugations viewed 30 deg off axis reduce the return loss below -35 dB. Ruthenium oxide resistive thermometers embedded within the absorber monitor the temperature across the face of the calibrator. The thermal calibration transfers the calibration of a reference thermometer to the flight thermometers using the flight thermometer readout system. Data taken near the superfluid transition in 8 independent calibrations 4 years apart agree within 0.3 mK, providing an independent verification of the thermometer calibration at temperatures near that of the cosmic microwave background.

  8. Synergetic use of millimeter- and centimeter-wavelength radars for retrievals of cloud and rainfall parameters

    Directory of Open Access Journals (Sweden)

    S. Y. Matrosov

    2010-04-01

    Full Text Available A remote sensing approach for simultaneous retrievals of cloud and rainfall parameters in the vertical column above the US Department of Energy's (DOE Climate Research Facility at the Tropical Western Pacific (TWP Darwin site in Australia is described. This approach uses vertically pointing measurements from a DOE Ka-band radar and scanning measurements from a nearby C-band radar pointing toward the TWP Darwin site. Rainfall retrieval constraints are provided by data from a surface impact disdrometer. The approach is applicable to stratiform precipitating cloud systems when a separation between the liquid hydrometeor layer, which contains rainfall and liquid water clouds, and the ice hydrometeor layer is provided by the radar bright band. Absolute C-band reflectivities and Ka-band vertical reflectivity gradients in the liquid layer are used for retrievals of the mean layer rain rate and cloud liquid water path (CLWP. C-band radar reflectivities are also used to estimate ice water path (IWP in regions above the melting layer. The retrieval uncertainties of CLWP and IWP for typical stratiform precipitation systems are about 500–800 g m−2 (for CLWP and a factor of 2 (for IWP. The CLWP retrieval uncertainties increase with rain rate, so retrievals for higher rain rates may be impractical. The expected uncertainties of layer mean rain rate retrievals are around 20%, which, in part, is due to constraints available from the disdrometer data. The applicability of the suggested approach is illustrated for two characteristic events observed at the TWP Darwin site during the wet season of 2007. A future deployment of W-band radars at the DOE tropical Climate Research Facilities can improve CLWP estimation accuracies and provide retrievals for a wider range of stratiform precipitating cloud events.

  9. The Radio Jet Associated with the Multiple V380 Ori System

    CERN Document Server

    Rodriguez, L F; Carrasco-Gonzalez, C; Anglada, G; Trejo, A

    2016-01-01

    The giant Herbig-Haro object 222 extends over $\\sim$6$'$ in the plane of the sky, with a bow shock morphology. The identification of its exciting source has remained uncertain over the years. A non-thermal radio source located at the core of the shock structure was proposed to be the exciting source. However, Very Large Array studies showed that the radio source has a clear morphology of radio galaxy and a lack of flux variations or proper motions, favoring an extragalactic origin. Recently, an optical-IR study proposed that this giant HH object is driven by the multiple stellar system V380 Ori, located about 23$'$ to the SE of HH 222. The exciting sources of HH systems are usually detected as weak free-free emitters at centimeter wavelengths. Here we report the detection of an elongated radio source associated with the Herbig Be star or with its close infrared companion in the multiple V380 Ori system. This radio source has the characteristics of a thermal radio jet and is aligned with the direction of the g...

  10. 21 Centimeter Tomography of the Intergalactic Medium at High Redshift

    Science.gov (United States)

    Madau, Piero; Meiksin, Avery; Rees, Martin J.

    1997-02-01

    We investigate the 21 cm signature that may arise from the intergalactic medium (IGM) prior to the epoch of full reionization (z > 5). In scenarios in which the IGM is reionized by discrete sources of photoionizing radiation, the neutral gas that has not yet been engulfed by an H II region may easily be preheated to temperatures well above that of the cosmic background radiation (CBR), rendering the IGM invisible in absorption against the CBR. We identify three possible preheating mechanisms: (1) photoelectric heating by soft X-rays from QSOs, (2) photoelectric heating by soft X-rays from early galactic halos, and (3) resonant scattering of the continuum UV radiation from an early generation of stars. We find that bright quasars with only a small fraction of the observed comoving density at z ~ 4 will suffice to preheat the entire universe at z >~ 6. We also show that, in a cold dark matter dominated cosmology, the thermal bremsstrahlung radiation associated with collapsing galactic mass halos (1010-1011 M⊙) may warm the IGM to ~100 K by z ~ 7. Alternatively, the equivalent of ~10% of the star formation rate density in the local universe, whether in isolated pregalactic stars, dwarf, or normal galaxies, would be capable of heating the entire IGM to a temperature above that of the CBR by Lyα scattering in a small fraction of the Hubble time at z ~ 6. In the presence of a sufficiently strong ambient flux of Lyα photons, the hyperfine transition in the warmed H I will be excited. A beam differencing experiment would detect a patchwork of emission, both in frequency and in angle across the sky. This patchwork could serve as a valuable tool for understanding the epoch, nature, and sources of the reionization of the universe, and their implications for cosmology. We demonstrate that isolated QSOs will produce detectable signals at meter wavelengths within their ``spheres of influence'' over which they warm the IGM. As a result of the redshifted 21 cm radiation

  11. Different evolutionary stages in massive star formation. Centimeter continuum and H2O maser emission with ATCA

    CERN Document Server

    Sanchez-Monge, A; Cesaroni, R; Fontani, F; Brand, J; Molinari, S; Testi, L; Burton, M

    2012-01-01

    We present ATCA observations of the H2O maser line and radio continuum at 18.0GHz and 22.8GHz, toward a sample of 192 massive star forming regions containing several clumps already imaged at 1.2mm. The main aim of this study is to investigate the water maser and centimeter continuum emission (likely tracing thermal free-free emission) in sources at different evolutionary stages, using the evolutionary classifications proposed by Palla et al (1991) and Molinari et al (2008). We used the recently comissioned CABB backend at ATCA obtaining images with 20arcsec resolution in the 1.3cm continuum and H2O maser emission, in all targets. For the evolutionary analysis of the sources we used the millimeter continuum emission from Beltran et al (2006) and the infrared emission from the MSX Point Source Catalogue. We detect centimeter continuum emission in 88% of the observed fields with a typical rms noise level of 0.45mJy/beam. Most of the fields show a single radio continuum source, while in 20% of them we identify mu...

  12. 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.

  13. Wavelength Converters

    DEFF Research Database (Denmark)

    Kloch, Allan; Hansen, Peter Bukhave; Wolfson, David;

    1999-01-01

    After a short introduction to the different requirements to and techniques for wavelength conversion, focus is on cross-gain and cross-phase modulation in SOAs and SOA based interferometers. Aspects like jitter accumulation, regeneration and conversion to the same wavelength is discussed. It is...... extinction ratio of ~10 dB.The regenerative capabilities of the cross-phase converters are described and verified experimentally at 20 Gbit/s, where the noise redistribution and improvement of the signal-to-noise ratio clearly is demonstrated by controlling the input power to an EDFA. In a similar experiment...

  14. Pre- and Post-burst Radio Observations of the Class 0 Protostar HOPS 383 in Orion

    CERN Document Server

    Galván-Madrid, Roberto; Liu, Hauyu B; Costigan, Gráinne; Palau, Aina; Zapata, Luis A; Loinard, Laurent; .,

    2015-01-01

    There is increasing evidence that episodic accretion is a common phenomenon in Young Stellar Objects (YSOs). Recently, the source HOPS 383 in Orion was reported to have a $\\times 35$ mid-infrared -- and bolometric -- luminosity increase between 2004 and 2008, constituting the first clear example of a class 0 YSO (a protostar) with a large accretion burst. The usual assumption that in YSOs accretion and ejection follow each other in time needs to be tested. Radio jets at centimeter wavelengths are often the only way of tracing the jets from embedded protostars. We searched the Very Large Array archive for the available observations of the radio counterpart of HOPS 383. The data show that the radio flux of HOPS 383 varies only mildly from January 1998 to December 2014, staying at the level of $\\sim 200$ to 300 $\\mu$Jy in the X band ($\\sim 9$ GHz), with a typical uncertainty of 10 to 20 $\\mu$Jy in each measurement. We interpret the absence of a radio burst as suggesting that accretion and ejection enhancements d...

  15. The Southern Twenty-centimeter All-sky Polarization Survey (STAPS)

    Science.gov (United States)

    Haverkorn, Marijke; Gaensler, Bryan; McConnell, David; McClure-Griffiths, Naomi; Carretti, Ettore; Kesteven, Michael; Wolleben, Maik; Heiles, Carl

    2009-10-01

    This is the fourth semester proposal for the large project P624, the Southern Twenty-centimeter All-sky Polarization Survey (STAPS), a 1.4GHz broadband all-sky survey which started as a piggy-back survey on the 2.3GHz survey S-PASS (P560). STAPS/S-PASS take data in long azimuth scans at fixed elevation. Starting times of scans are determined exactly, so that scans cover adjacent bands across the sky, eventually resulting in a Nyquist-coverage of the southern sky. The science goals of STAPS focus on the Galactic interstellar medium and magnetism. Using rotation measure synthesis, we can disentangle synchrotron emitting and Faraday rotating sources along the line of sight, allowing a new view of the polarized radio sky. The data will be used to advance models of the large-scale Galactic magnetic field, for characterization of depolarization and interstellar turbulence and for studies of magnetism in discrete structures such as supernova remnants. On- and off-axis instrumental polarization will be characterized and removed. Initial calibration indicates on-axis instrumental polarization of about one percent, which is expected to go down using more sophisticated calibration methods.

  16. Centimeter Polarimetry of the R Coronae Australis Region

    OpenAIRE

    Choi, Minho; Tatematsu, Ken'ichi; Hamaguchi, Kenji; Lee, Jeong-Eun

    2008-01-01

    Circularly polarized 3.5 cm continuum emission was detected toward three radio sources in the R CrA region using the Very Large Array. The Class I protostar IRS 5b persistently showed polarized radio emission with a constant helicity over 8 yr, which suggests that its magnetosphere has a stable configuration. There is a good correlation between the Stokes I and Stokes V fluxes, and the fractional polarization is about 0.17. During active phases the fractional polarization is a weakly decreasi...

  17. The empirical difference between radio-loud and radio-quiet quasars

    International Nuclear Information System (INIS)

    Lobe-dominant radio quasars and radio-quiet quasars have very similar spectral energy distributions in the infrared through ultraviolet spectral regions. The former class show flat-spectrum radio synchrotron cores as well. Are the radio cores the self-absorbed tails of nonthermal infrared sources, or are they separate components with properties expected for misdirected relativistic jets? Morphologically, do the spectra peak in the millimeter region as expected under the first hypothesis, or do they show deep minima there as expected under the second? Centimeter, infrared, and new millimeter observations show that the second hypothesis is correct for all six known IRAS-detected lobe-dominant quasars. 20 refs

  18. Radio and gamma-ray follow-up of the exceptionally high activity state of PKS 1510-089 in 2011

    CERN Document Server

    Orienti, M; D'Ammando, F; Giroletti, M; Kino, M; Nagai, H; Venturi, T; Dallacasa, D; Giovannini, G; Angelakis, E; Fuhrmann, L; Hovatta, T; Max-Moerbeck, W; Schinzel, F K; Akiyama, K; Hada, K; Honma, M; Niinuma, K; Gasparrini, D; Krichbaum, T P; Nestoras, I; Readhead, A C S; Richards, J L; Riquelme, D; Sievers, A; Ungerechts, H; Zensus, J A

    2012-01-01

    We investigate the radio and gamma-ray variability of the flat spectrum radio quasar PKS 1510-089 in the time range between 2010 November and 2012 January. In this period the source showed an intense activity, with two major gamma-ray flares detected in 2011 July and October. During the latter episode both the gamma-ray and the radio flux density reached their historical peak. Multiwavelength analysis shows a rotation of about 380 deg of the optical polarization angle close in time with the rapid and strong gamma-ray flare in 2011 July. An enhancement of the optical emission and an increase of the fractional polarization both in the optical and in radio bands is observed about three weeks later, close in time with another gamma-ray outburst. On the other hand, after 2011 September a huge radio outburst has been detected, first in the millimeter regime followed with some time delay at centimeter down to decimeter wavelengths. This radio flare is characterized by a rising and a decaying stage, in agreement with...

  19. Low noise frequency synthesizer of a centimeter range wave

    Directory of Open Access Journals (Sweden)

    I. S. Tsvelikh

    2007-06-01

    Full Text Available A highly stable, low noise 10.7 GHz frequency synthesizer for radio-relay link transceiver is presented. The basic elements of synthesizer are electrically tuned 5.35 GHz dielectric ring oscillator and transistor frequency doubler.

  20. Radio flux flicker of extragalactic sources

    International Nuclear Information System (INIS)

    The author describes observations which indicate that compact sources (compactness evidenced by flat/complex spectra) display a ''flicker'' in their intrinsic centimeter wavelength radiation, with an amplitude of about 2% and a characteristic time scale of a few days. (Auth.)

  1. The Evolving Radio Jet in BL Lacerta

    Science.gov (United States)

    Aller, H. D.; Hughes, P. A.; Aller, M. F.

    1994-05-01

    During the past 15 years, there have been at least ten outbursts at centimeter wavelengths in this extragalactic object. We describe here the flux density and linear polarization variations observed at 4.8, 8.0 and 14.5 GHz with the Michigan 26-meter telescope during the series of outbursts since 1987. The recent bursts are somewhat different from the highly polarized bursts in the early 1980s, which provided a successful quantitative test of a source model based on propagating transverse shocks in a relativistic jet. The most notable change is that the polarization position angle during polarized outbursts has increased by approximately 10 degrees. This is approximately the same shift as found in a comparison of VLBI maps taken during the same time periods by Mutel, Denn and Dryer (1994, NRAO Workshop on Compact Extragalactic Radio Sources, ed. Zensus and Kellermann, p. 191), and supports their conclusion that the orientation of the radio emitting jet in BL Lac has changed over time. Our preliminary analysis further suggests that a simple scaling of the physical parameters which gave quantitatively good fits to both the 1982 and 1983 bursts will not accurately describe the recent, relatively isolated, burst in 1991. We also note that while some bursts (e.g. in 1982, 1983 and 1991) exhibit degrees of linear polarization in excess of ten percent, other bursts (e.g. in 1980 and 1990) exhibit a very low degree of linear polarization. A common characteristic of the low polarization events is that they all exhibit high internal synchrotron self absorption (as indicated by the flux density spectra of the outbursts). This research has been supported in part by NSF grant AST-9120224.

  2. Low-velocity collisions of centimeter-sized dust aggregates

    CERN Document Server

    Beitz, Eike; Blum, Jürgen; Meisner, Thorsten; Teiser, Jens; Wurm, Gerhard

    2011-01-01

    Collisions between centimeter- to decimeter-sized dusty bodies are important to understand the mechanisms leading to the formation of planetesimals. We thus performed laboratory experiments to study the collisional behavior of dust aggregates in this size range at velocities below and around the fragmentation threshold. We developed two independent experimental setups with the same goal to study the effects of bouncing, fragmentation, and mass transfer in free particle-particle collisions. The first setup is an evacuated drop tower with a free-fall height of 1.5 m, providing us with 0.56 s of microgravity time so that we observed collisions with velocities between 8 mm/s and 2 m/s. The second setup is designed to study the effect of partial fragmentation (when only one of the two aggregates is destroyed) and mass transfer in more detail. It allows for the measurement of the accretion efficiency as the samples are safely recovered after the encounter. Our results are that for very low velocities we found bounc...

  3. Prototype for Long Wavelength Array Sees First Light

    Science.gov (United States)

    2007-03-01

    and dark energy." Although radio astronomy was discovered at low frequencies (near 20 MHz, corresponding to wavelengths of 15 meters), well below the current FM band, astronomers quickly moved up to higher frequencies (centimeter wavelengths) in search of higher resolution and to escape the corrupting effects of the Earth's ionosphere, a region of charged particles between about 50 and 600 miles above the surface. The ionosphere, which can "bend" radio waves to produce long-distance reception of AM and short-wave radio signals, also causes distortions in radio telescope images in much the same way that atmospheric irregularities cause twinkling of stars. Ionospheric effects become much worse at low frequencies, but new imaging techniques developed at NRL and elsewhere have allowed the "ionospheric barrier" to be broken and enabled high-resolution astronomical imaging at these low frequencies for the first time. These new imaging techniques provide an improved view of not only the astronomical sky, but the Earth's ionosphere as well. The full LWA will generate richly detailed measurements of the ionosphere that will complement other ionospheric data sources. Understanding the ionosphere is critically important to the Department of Defense because of its effects on communications and navigation systems. The current prototype, referred to as the Long Wavelength Demonstrator Array (LWDA) to differentiate it from the larger LWA project, completed installation on the Plains of San Agustin in southwestern New Mexico in the fall of 2006. Funded by NRL and built by the Applied Research Laboratories of the University of Texas, Austin (ARL:UT), the telescope consists of 16 antennas connected to a suite of electronics that combine the signals from each antenna. Each antenna is only 4 feet tall and acts much like an old style television antenna, receiving radio waves from many different directions simultaneously. When combined, the data from the individual antennas is comparable

  4. Centimeter Cosmo-Skymed Range Measurements for Monitoring Ground Displacements

    Science.gov (United States)

    Fratarcangeli, F.; Nascetti, A.; Capaldo, P.; Mazzoni, A.; Crespi, M.

    2016-06-01

    The SAR (Synthetic Aperture Radar) imagery are widely used in order to monitor displacements impacting the Earth surface and infrastructures. The main remote sensing technique to extract sub-centimeter information from SAR imagery is the Differential SAR Interferometry (DInSAR), based on the phase information only. However, it is well known that DInSAR technique may suffer for lack of coherence among the considered stack of images. New Earth observation SAR satellite sensors, as COSMO-SkyMed, TerraSAR-X, and the coming PAZ, can acquire imagery with high amplitude resolutions too, up to few decimeters. Thanks to this feature, and to the on board dual frequency GPS receivers, allowing orbits determination with an accuracy at few centimetres level, the it was proven by different groups that TerraSAR-X imagery offer the capability to achieve, in a global reference frame, 3D positioning accuracies in the decimeter range and even better just exploiting the slant-range measurements coming from the amplitude information, provided proper corrections of all the involved geophysical phenomena are carefully applied. The core of this work is to test this methodology on COSMO-SkyMed data acquired over the Corvara area (Bolzano - Northern Italy), where, currently, a landslide with relevant yearly displacements, up to decimeters, is monitored, using GPS survey and DInSAR technique. The leading idea is to measure the distance between the satellite and a well identifiable natural or artificial Persistent Scatterer (PS), taking in account the signal propagation delays through the troposphere and ionosphere and filtering out the known geophysical effects that induce periodic and secular ground displacements. The preliminary results here presented and discussed indicate that COSMO-SkyMed Himage imagery appear able to guarantee a displacements monitoring with an accuracy of few centimetres using only the amplitude data, provided few (at least one) stable PS's are available around the

  5. RU Radio

    OpenAIRE

    Ahlbom, Anna Lohmann; Bollmann, Anders Theis; Mariager, Casper

    2012-01-01

    The point of departure in this report is the newly established student radio at Roskilde University named RU Radio. The radio was established in 2012. This report aims to device an editorial policy for RU Radio. The report starts with a clarification of the conditions of RU Radio. Following is a discussion of the press and media ethics in relation to RU Radio which juxtaposed with more concrete ethical guidelines. Accordingly attempts are made to define the radio audience and to clarify their...

  6. An Exceptional Radio Flare in Markarian 421

    CERN Document Server

    Richards, Joseph L; Lister, Matthew L; Readhead, Anthony C S; Max-Moerbeck, Walter; Savolainen, Tuomas; Angelakis, Emmanouil; Fuhrmann, Lars; Aller, Margo F; Aller, Hugh D

    2013-01-01

    In September 2012, the high-synchrotron-peaked (HSP) blazar Markarian 421 underwent a rapid wideband radio flare, reaching nearly twice the brightest level observed in the centimeter band in over three decades of monitoring. In response to this event we carried out a five epoch centimeter- to millimeter-band multifrequency Very Long Baseline Array (VLBA) campaign to investigate the aftermath of this emission event. Rapid radio variations are unprecedented in this object and are surprising in an HSP BL Lac object. In this flare, the 15 GHz flux density increased with an exponential doubling time of about 9 days, then faded to its prior level at a similar rate. This is comparable with the fastest large-amplitude centimeter-band radio variability observed in any blazar. Similar flux density increases were detected up to millimeter bands. This radio flare followed about two months after a similarly unprecedented GeV gamma-ray flare (reaching a daily E>100 MeV flux of (1.2 +/- 0.7)x10^(-6) ph cm^(-2) s^(-1)) repor...

  7. The Population of Compact Radio Sources in the Orion Nebula Cluster

    CERN Document Server

    Forbrich, Jan; Menten, Karl M; Reid, Mark J; Chandler, Claire J; Rau, Urvashi; Bhatnagar, Sanjay; Wolk, Scott J; Meingast, Stefan

    2016-01-01

    We present a deep centimeter-wavelength catalog of the Orion Nebula Cluster (ONC), based on a 30h single-pointing observation with the Karl G. Jansky Very Large Array in its high-resolution A-configuration using two 1 GHz bands centered at 4.7 GHz and 7.3 GHz. A total of 556 compact sources were detected in a map with a nominal rms noise of 3 muJy/bm, limited by complex source structure and the primary beam response. Compared to previous catalogs, our detections increase the sample of known compact radio sources in the ONC by more than a factor of seven. The new data show complex emission on a wide range of spatial scales. Following a preliminary correction for the wideband primary-beam response, we determine radio spectral indices for 170 sources whose index uncertainties are less than +/-0.5. We compare the radio to the X-ray and near-infrared point-source populations, noting similarities and differences.

  8. The Population of Compact Radio Sources in the Orion Nebula Cluster

    Science.gov (United States)

    Forbrich, J.; Rivilla, V. M.; Menten, K. M.; Reid, M. J.; Chandler, C. J.; Rau, U.; Bhatnagar, S.; Wolk, S. J.; Meingast, S.

    2016-05-01

    We present a deep centimeter-wavelength catalog of the Orion Nebula Cluster (ONC), based on a 30 hr single-pointing observation with the Karl G. Jansky Very Large Array in its high-resolution A-configuration using two 1 GHz bands centered at 4.7 and 7.3 GHz. A total of 556 compact sources were detected in a map with a nominal rms noise of 3 μJy bm-1, limited by complex source structure and the primary beam response. Compared to previous catalogs, our detections increase the sample of known compact radio sources in the ONC by more than a factor of seven. The new data show complex emission on a wide range of spatial scales. Following a preliminary correction for the wideband primary-beam response, we determine radio spectral indices for 170 sources whose index uncertainties are less than ±0.5. We compare the radio to the X-ray and near-infrared point-source populations, noting similarities and differences.

  9. Free-space wavelength-multiplexed optical scanner.

    Science.gov (United States)

    Yaqoob, Z; Rizvi, A A; Riza, N A

    2001-12-10

    A wavelength-multiplexed optical scanning scheme is proposed for deflecting a free-space optical beam by selection of the wavelength of the light incident on a wavelength-dispersive optical element. With fast tunable lasers or optical filters, this scanner features microsecond domain scan setting speeds and large- diameter apertures of several centimeters or more for subdegree angular scans. Analysis performed indicates an optimum scan range for a given diffraction order and grating period. Limitations include beam-spreading effects based on the varying scanner aperture sizes and the instantaneous information bandwidth of the data-carrying laser beam. PMID:18364951

  10. The nighttime ionosphere of Mars from Mars-4 and Mars-5 radio occultation dual-frequency measurements

    Science.gov (United States)

    Savich, N. A.; Samovol, V. A.; Vasilyev, M. B.; Vyshlov, A. S.; Samoznaev, L. N.; Sidorenko, A. I.; Shtern, D. Y.

    1976-01-01

    Dual frequency radio sounding of the Martian nighttime ionosphere was carried out during the exits from behind the planet of the Mars-4 spacecraft on February 2, 1974 and the Mars-5 spacecraft on February 18, 1974. In these experiments, the spacecraft transmitter emitted two coherent monochromatic signals in decimeter and centimeter wavelength ranges. At the Earth receiving station, the reduced phase difference (or frequencies) of these signals was measured. The nighttime ionosphere of Mars measured in both cases had a peak electron density of approximately 5 X 1,000/cu cm at an altitude of 110 to 130 km. At the times of spacecraft exit, the solar zenith angles at the point of occultation were 127 deg and 106 deg, respectively. The height profiles of electron concentration were obtained assuming spherical symmetry of the Martian ionosphere.

  11. Radio Astronomy in LSST Era

    CERN Document Server

    Lazio, T Joseph W; Barger, A J; Brandt, W N; Chatterjee, S; Clarke, T E; Condon, J J; Dickman, Robert L; Hunyh, M T; Jarvis, Matt J; Juric, Mario; Kassim, N E; Myers, S T; Nissanke, Samaya; Osten, Rachel; Zauderer, B A

    2014-01-01

    A community meeting on the topic of "Radio Astronomy in the LSST Era" was hosted by the National Radio Astronomy Observatory in Charlottesville, VA (2013 May 6--8). The focus of the workshop was on time domain radio astronomy and sky surveys. For the time domain, the extent to which radio and visible wavelength observations are required to understand several classes of transients was stressed, but there are also classes of radio transients for which no visible wavelength counterpart is yet known, providing an opportunity for discovery. From the LSST perspective, the LSST is expected to generate as many as 1 million alerts nightly, which will require even more selective specification and identification of the classes and characteristics of transients that can warrant follow up, at radio or any wavelength. The LSST will also conduct a deep survey of the sky, producing a catalog expected to contain over 38 billion objects in it. Deep radio wavelength sky surveys will also be conducted on a comparable time scale,...

  12. Change of slope s-component of the solar radio emission as a harbinger of the powerful solar flares

    International Nuclear Information System (INIS)

    Full text : Registration of the fluctuations of the solar radio emission is one of the ways to study the wave and turbulent processes occurring on the Sun. It is known that the radio spectrographic measurements of the radio emission of the Sun provide a wealth of information on the physical conditions in the vast regions of the Sun, from the chromosphere to the super-corona. In his paper we give a brief overview of radio spectrographic measurements of the quiet and active solar radio emission. In particular, at the Institute of Radio Physics in Russia, Professor M.M. Kobrin found the fine structure of the S-component the solar radio emission in the range of 4 - 12 GHz. It has been speculated that the fine structure can exist in the longer wavelength part of the centimeter range, and in the short-wave range. To test this hypothesis it was constructed the radio spectrographs based on the domestic receivers in the range of 1-2 GHz and 2-4 GHz and conducted extensive observations with RT-7.5, RT-12 Ionosphere Institute, Academy of Sciences of the Republic of Kazakhstan and RT-22. It is known that the shape of the spectrum allows to judge about the role of a mechanism responsible for the radio emission of the Sun. Study of the structure of the frequency spectrum of S-component of the Sun and its changes provide information about the relatively slow processes in the local sources at formation there the conditions for the emergence of powerful flares. Analysis of data derived from the slopes of the spectra in the moments preceding these events, allowed to make the following conclusions: 1. short-modulation spectral slope of S-component of the solar radio emission with changes about 7 x t and 15 minutes has a small amplitude and spectrum of the fine structure been weakened; 2. for 1-3 days prior to the powerful flash the slope of the S-component of solar radio emission with a change of temperature within 20 - 35 minutes have a higher amplitude in the spectra and the fine

  13. SIMULTANEOUS MULTI-WAVELENGTH OBSERVATIONS OF Sgr A* DURING 2007 APRIL 1-11

    International Nuclear Information System (INIS)

    We report the detection of variable emission from Sgr A* in almost all wavelength bands (i.e., centimeter, millimeter, submillimeter, near-IR, and X-rays) during a multi-wavelength observing campaign. Three new moderate flares are detected simultaneously in both near-IR and X-ray bands. The ratio of X-ray to near-IR flux in the flares is consistent with inverse Compton scattering of near-IR photons by submillimeter emitting relativistic particles which follow scaling relations obtained from size measurements of Sgr A*. We also find that the flare statistics in near-IR wavelengths is consistent with the probability of flare emission being inversely proportional to the flux. At millimeter wavelengths, the presence of flare emission at 43 GHz (7 mm) using the Very Long Baseline Array with milliarcsecond spatial resolution indicates the first direct evidence that hourly timescale flares are localized within the inner 30 x 70 Schwarzschild radii of Sgr A*. We also show several cross-correlation plots between near-IR, millimeter, and submillimeter light curves that collectively demonstrate the presence of time delays between the peaks of emission up to 5 hr. The evidence for time delays at millimeter and submillimeter wavelengths are consistent with the source of emission initially being optically thick followed by a transition to an optically thin regime. In particular, there is an intriguing correlation between the optically thin near-IR and X-ray flare and optically thick radio flare at 43 GHz that occurred on 2007 April 4. This would be the first evidence of a radio flare emission at 43 GHz delayed with respect to the near-IR and X-ray flare emission. The time delay measurements support the expansion of hot self-absorbed synchrotron plasma blob and weaken the hot spot model of flare emission. In addition, a simultaneous fit to 43 and 84 GHz light curves, using an adiabatic expansion model of hot plasma, appears to support a power law rather than a relativistic

  14. Phenomenology of magnetospheric radio emissions

    Science.gov (United States)

    Carr, T. D.; Desch, M. D.; Alexander, J. K.

    1983-01-01

    Jupiter has now been observed over 24 octaves of the radio spectrum, from about 0.01 MHz to 300,000 MHz. Its radio emissions fill the entire spectral region where interplanetary electromagnetic propagation is possible at wavelengths longer than infrared. Three distinct types of radiation are responsible for this radio spectrum. Thermal emission from the atmosphere accounts for virtually all the radiation at the high frequency end. Synchrotron emission from the trapped high-energy particle belt deep within the inner magnetosphere is the dominant spectral component from about 4000 to 40 MHz. The third class of radiation consists of several distinct components of sporadic low frequency emission below 40 MHz. The decimeter wavelength emission is considered, taking into account the discovery of synchrotron emission, radiation by high-energy electrons in a magnetic field, and the present status of Jovian synchrotron phenomenology. Attention is also given to the decameter and hectometer wavelength emission, and emissions at kilometric wavelengths.

  15. Techniques of Radio Astronomy

    CERN Document Server

    Wilson, T L

    2011-01-01

    This chapter provides an overview of the techniques of radio astronomy. This study began in 1931 with Jansky's discovery of emission from the cosmos, but the period of rapid progress began fifteen years later. From then to the present, the wavelength range expanded from a few meters to the sub-millimeters, the angular resolution increased from degrees to finer than milli arc seconds and the receiver sensitivities have improved by large factors. Today, the technique of aperture synthesis produces images comparable to or exceeding those obtained with the best optical facilities. In addition to technical advances, the scientific discoveries made in the radio range have contributed much to opening new visions of our universe. There are numerous national radio facilities spread over the world. In the near future, a new era of truly global radio observatories will begin. This chapter contains a short history of the development of the field, details of calibration procedures, coherent/heterodyne and incoherent/bolom...

  16. Sub-millimeter to centimeter excess emission from the Magellanic Clouds. I. Global spectral energy distribution

    CERN Document Server

    Israel, F P; Raban, D; Reach, W T; Bot, C; Oonk, J B R; Ysard, N; Bernard, J P

    2010-01-01

    In order to reconstruct the global SEDs of the Magellanic Clouds over eight decades in spectral range, we combined literature flux densities representing the entire LMC and SMC respectively, and complemented these with maps extracted from the WMAP and COBE databases covering the missing the 23--90 GHz (13--3.2 mm) and the poorly sampled 1.25--250 THz (240--1.25 micron). We have discovered a pronounced excess of emission from both Magellanic Clouds, but especially the SMC, at millimeter and sub-millimeter wavelengths. We also determined accurate thermal radio fluxes and very low global extinctions for both LMC and SMC. Possible explanations are briefly considered but as long as the nature of the excess emission is unknown, the total dust masses and gas-to-dust ratios of the Magellanic Clouds cannot reliably be determined.

  17. 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

    International Nuclear Information System (INIS)

    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+17−11 new radio sources brighter than 0.87 mJy at 30 GHz in a 1 deg2 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-deg2 survey, with field coverage of 22 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 × 104 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 × 105 radio sources at 5σ CL down to 1.3 mJy, and tens of galaxy clusters, in one year of operation with

  18. 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.

  19. An Exceptional Radio Flare in Markarian 421

    Directory of Open Access Journals (Sweden)

    Richards Joseph L.

    2013-12-01

    Full Text Available In September 2012, the high-synchrotron-peaked (HSP blazar Markarian 421 underwent a rapid wideband radio flare, reaching nearly twice the brightest level observed in the centimeter band in over three decades of monitoring. In response to this event we carried out a five epoch centimeter- to millimeter-band multifrequency Very Long Baseline Array (VLBA campaign to investigate the aftermath of this emission event. Rapid radio variations are unprecedented in this object and are surprising in an HSP BL Lac object. In this flare, the 15 GHz flux density increased with an exponential doubling time of about 9 days, then faded to its prior level at a similar rate. This is comparable with the fastest large-amplitude centimeter-band radio variability observed in any blazar. Similar flux density increases were detected up to millimeter bands. This radio flare followed about two months after a similarly unprecedented GeV gamma-ray flare (reaching a daily E > 100 MeV flux of (1.2 ± 0.7 × 10−6 ph cm−2 s−1 reported by the Fermi Large Area Telescope (LAT collaboration, with a simultaneous tentative TeV detection by ARGO-YBJ. A cross-correlation analysis of long-term 15 GHz and LAT gamma-ray light curves finds a statistically significant correlation with the radio lagging ~40 days behind, suggesting that the gamma-ray emission originates upstream of the radio emission. Preliminary results from our VLBA observations show brightening in the unresolved core region and no evidence for apparent superluminal motions or substantial flux variations downstream.

  20. Radio Flaring from the T6 Dwarf WISEPC J112254.73+255021.5 with a Possible Ultra-short Periodicity

    Science.gov (United States)

    Route, Matthew; Wolszczan, Alexander

    2016-04-01

    We present new results from a continuing 5 GHz search for flaring radio emission from a sample of L and T brown dwarfs, conducted with the 305 m Arecibo radio telescope. In addition to the previously reported flaring from the T6.5 dwarf 2MASS J10475385+212423, we have detected and confirmed circularly polarized flares from another T6 dwarf, WISEPC J112254.73+255021.5. Although the flares are sporadic, they appear to occur at a stable period of 0.288 hr. Given the current constraints, periods equal to its second and third subharmonic cannot be ruled out. The stability of this period over the eight-month timespan of observations indicates that, if real, it likely reflects the star’s rapid rotation. If confirmed, any of the three inferred periodicities would be much shorter than the shortest, 1.41 hr, rotation period of a brown dwarf measured so far. This finding would place a new observational constraint on the angular momentum evolution and rotational stability of substellar objects. The detection of radio emission from the sixth ∼1000 K dwarf further demonstrates that the coolest brown dwarfs and, possibly, young giant planets, can be efficiently investigated using radio observations at centimeter wavelengths as a tool.

  1. 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

  2. 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.

  3. 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.

  4. Wavelength converter technology

    DEFF Research Database (Denmark)

    Kloch, Allan; Hansen, Peter Bukhave; Poulsen, Henrik Nørskov;

    1999-01-01

    Wavelength conversion is important since it ensures full flexibility of the WDM network layer. Progress in optical wavelength converter technology is reviewed with emphasis on air-optical wavelength converter types based on semiconductor optical amplifiers....

  5. Wavelength converter technology

    DEFF Research Database (Denmark)

    Kloch, Allan; Hansen, Peter Bukhave; Poulsen, Henrik Nørskov; Wolfson, David; Jepsen, Kim Stokholm; Clausen, Anders; Limal, Emmanuel; Buxens, Alvaro A.

    Wavelength conversion is important since it ensures full flexibility of the WDM network layer. Progress in optical wavelength converter technology is reviewed with emphasis on air-optical wavelength converter types based on semiconductor optical amplifiers.......Wavelength conversion is important since it ensures full flexibility of the WDM network layer. Progress in optical wavelength converter technology is reviewed with emphasis on air-optical wavelength converter types based on semiconductor optical amplifiers....

  6. Radio Reconstructions

    OpenAIRE

    Bulley, James; Jones, Daniel

    2013-01-01

    Radio Reconstructions is a sound installation which use indeterminate radio broadcasts as its raw material. Each piece is structured by a notated score, which controls its rhythm, dynamics and melodic contour over time. The audio elements used to enact this score are selected in real-time from unknown radio transmissions, by an autonomous software system which is continuously scanning the radio waves in search of similar fragments of audio. Using a technique known as audio mosaicing, hund...

  7. Radio Ghosts

    OpenAIRE

    Ensslin, Torsten A.

    1999-01-01

    We investigate the possibility that patches of old radio plasma (`radio ghosts') of former radio galaxies form a second distinct phase of the inter-galactic medium (IGM), not mixed with the thermal gas. The separation of this phase from the ambient gas and its resistance against eroding turbulent forces is given by magnetic fields, which are expected to be roughly in pressure equilibrium with the surrounding medium. Since patches of this plasma are largely invisible in the radio we use the te...

  8. Radio astronomy

    International Nuclear Information System (INIS)

    This report highlights radio astronomy research of the 40th IAU commission in the years 1982-1984. Radio imaging of different objects are treated in separate sections: solar system, galaxy, supernovae, extragalactic objects. The paper begins with a section on radio instrumentation

  9. X-ray Properties of Deep Radio-Selected Quasars

    Science.gov (United States)

    Becker, Robert

    2002-01-01

    This report summarizes the research supported by the ADP grant entitled 'X-ray Properties of Deep Radio-Selected Quasars'. The primary effort consisted of correlating the ROSAT All-Sky Survey catalog with the April 1997 release of the FIRST (Faint Images of the Radio Sky at Twenty centimeters) radio catalog. We found that a matching radius of 60 sec excluded most false matches while retaining most of the true radio-X-ray sources. The correlation of the approx. 80,000 source RASS and approx. 268,000 FIRST catalogs matched 2,588 FIRST sources with 1,649 RASS sources out of a possible 5,520 RASS sources residing in the FIRST survey area. This number is much higher than expected from our previous experience of correlating the RASS with radio surveys and indicates we detected new classes of objects not seen in the correlations with less sensitive radio surveys.

  10. Wavelength conversion devices

    DEFF Research Database (Denmark)

    Mikkelsen, Benny; Durhuus, Terji; Jørgensen, Carsten;

    1996-01-01

    Summary form only given. Wavelength converters will be essential devices to exploit the full potential of the wavelength dimension in wavelength-division multiplexed (WDM) networks. Based on experiments, we discuss different candidates for efficient wavelength converters with attention to expected...

  11. Dynamic Outer Loop Link Adaptation for the 5G Centimeter-Wave Concept

    DEFF Research Database (Denmark)

    Gatnau, Marta; Catania, Davide; Frederiksen, Frank;

    2015-01-01

    A 5th generation (5G) of wireless communication systems is expected to be introduced around 2020 to cope with a rapid increase of mobile data traffic. One of the main challenges of our envisioned 5G centimeter-wave concept is a large signal to interference plus noise ratio (SINR) variability, due...

  12. Radio wave.

    Science.gov (United States)

    Elkin, V

    1992-01-01

    In developing countries with high rates of poverty and illiteracy, radio is emerging as an excellent medium for delivering information on health issues, family planning, nutrition, and agricultural development. Since radio does not require wired electricity, it can reach remote rural populations. Surveys have found that between 50-75% of poor rural households in developing countries own radios, and the majority listen to educational radio at least once a week. A program that reaches the urban poor outside of Lima, Peru, has been instrumental in controlling the spread of cholera. A Bolivian station broadcasts 8 hours of literacy, health, agricultural, and cultural programming a day to an audience of more than 2 million Aymara Indians. Small village radio stations with a broadcast range of 15 miles can be established for under US$400 and can generally achieve sustainability through local fundraising events such as raffles. In many cases, listeners have become broadcasters at their local radio stations. PMID:12286181

  13. Radio receivers

    Science.gov (United States)

    Bankov, V. N.; Barulin, L. G.; Zhodzishskii, M. I.; Malyshev, I. V.; Petrusinskii, V. V.

    The book is concerned with the design of microelectronic radio receivers and their components based on semiconductor and hybrid integrated circuits. Topics discussed include the hierarchical structure of radio receivers, the synthesis of structural schemes, the design of the principal functional units, and the design of radio receiver systems with digital signal processing. The discussion also covers the integrated circuits of multifunctional amplifiers, analog multipliers, charge-transfer devices, frequency filters, piezoelectronic devices, and microwave amplifiers, filters, and mixers.

  14. Measurement of radio networks, depending on the profile of landscape

    OpenAIRE

    PEČINKA, Miroslav

    2014-01-01

    This thesis describes a brief history of radio and electromagnetic waves from a physical point of view. It focuses mainly on radio waves in the VHF and subsequent construction of a radio network in this band. It uses the knowledge of the writer of this wavelength. This thesis is intended as a guide for fellow author.

  15. 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...

  16. Radio stars.

    Science.gov (United States)

    Hjellming, R M; Wade, C M

    1971-09-17

    Up to the present time six classes of radio stars have been established. The signals are almost always very faint and drastically variable. Hence their discovery has owed as much to serendipity as to the highly sophisticated equipment and techniques that have been used. When the variations are regular, as with the pulsars, this characteristic can be exploited very successfully in the search for new objects as well as in the detailed study of those that are already known. The detection of the most erratically variable radio stars, the flare stars and the x-ray stars, is primarily a matter of luck and patience. In the case of the novas, one at least knows where and oughly when to look for radio emission. A very sensitive interferometer is clearly the best instrument to use in the initial detection of a radio star. The fact that weak background sources are frequently present makes it essential to prove that the position of a radio source agrees with that of a star to within a few arc seconds. The potential of radio astronomy for the study of radio stars will not be realized until more powerful instruments than those that are available today can be utilized. So far, we have been able to see only the most luminous of the radio stars. PMID:17836594

  17. Characteristics of the wavelength of ripples on icicles

    CERN Document Server

    Ueno, K

    2011-01-01

    It is known that the wavelength of the ripples on icicles in nature is of centimeter-scale. Such study on morphological instability of ice-water interface during ice growth from flowing supercooled water film with one side being a free surface has recently been made [K. Ueno, Phys. Rev. E 68, 021603 (2003)]. This is a first theoretical study taking into account the influence of the shape of the water-air surface on the growth condition of infinitesimal disturbances of the ice-water interface. A simpler formula to determine the wavelength of the ripples than that in the previous paper is derived. It seems that the wavelength of ripples is insensitive to the water supply rates, diameters of the icicles and surrounding air temperatures. The details of dependence of the wavelengh of ripples on these parameters are investigated.

  18. Ultrasound Indoor Positioning System Based on a Low-Power Wireless Sensor Network Providing Sub-Centimeter Accuracy

    Directory of Open Access Journals (Sweden)

    Ángel De la Torre

    2013-03-01

    Full Text Available This paper describes the TELIAMADE system, a new indoor positioning system based on time-of-flight (TOF of ultrasonic signal to estimate the distance between a receiver node and a transmitter node. TELIAMADE system consists of a set of wireless nodes equipped with a radio module for communication and a module for the transmission and reception of ultrasound. The access to the ultrasonic channel is managed by applying a synchronization algorithm based on a time-division multiplexing (TDMA scheme. The ultrasonic signal is transmitted using a carrier frequency of 40 kHz and the TOF measurement is estimated by applying a quadrature detector to the signal obtained at the A/D converter output. Low sampling frequencies of 17.78 kHz or even 12.31 kHz are possible using quadrature sampling in order to optimize memory requirements and to reduce the computational cost in signal processing. The distance is calculated from the TOF taking into account the speed of sound. An excellent accuracy in the estimation of the TOF is achieved using parabolic interpolation to detect of maximum of the signal envelope at the matched filter output. The signal phase information is also used for enhancing the TOF measurement accuracy. Experimental results show a root mean square error (rmse less than 2 mm and a standard deviation less than 0.3 mm for pseudorange measurements in the range of distances between 2 and 6 m. The system location accuracy is also evaluated by applying multilateration. A sub-centimeter location accuracy is achieved with an average rmse of 9.6 mm.

  19. Radio-Optical Alignments in a Low Radio Luminosity Sample

    Science.gov (United States)

    Lacy, Mark; Ridgway, Susan E.; Wold, Margrethe; Lilje, Per B.; Rawlings, Steve

    1999-01-01

    We present an optically-based study of the alignment between the radio axes and the optical major axes of eight z approximately 0.7 radio galaxies in a 7C sample. The radio galaxies in this sample are approximately 20-times less radio luminous than 3C galaxies at the same redshift, and are significantly less radio-luminous than any other well-defined samples studied to date. Using Nordic Optical Telescope images taken in good seeing conditions at rest-frame wavelengths just longward of the 4000A break, we find a statistically significant alignment effect in the 7C sample. Furthermore, in two cases where the aligned components are well separated from the host we have been able to confirm spectroscopically that they are indeed at the same redshift as the radio galaxy. However, a quantitative analysis of the alignment in this sample and in a corresponding 3C sample from HST (Hubble Space Telescope) archival data indicates that the percentage of aligned flux may be lower and of smaller spatial scale in the 7C sample. Our study suggests that alignments on the 50-kpc scale are probably closely related to the radio luminosity, whereas those on the 15 kpc scale are not. We discuss these results in the context of popular models for the alignment effect.

  20. Radio supernovae

    International Nuclear Information System (INIS)

    The authors report the radio detection of supernova 1961v in NGC 1058. SN 1961v has a spectral index of - 0.4 ±0.1. At the distance of NGC 1058, the absolute monochromatic luminosity of this source is comparable to that of Cas A. A second nonthermal source with a spectral index of - 0.3 ±0.1 was also detected in NGC 1058 and is likely to be a remnant of a supernova that was not optically detected. The two radio sources, and two optically faint H II regions that coincide with the radio sources, are separated by only 3.5 double-prime

  1. How long wavelengths can one extract from silica-core fibers?

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper; Tu, Haohua

    2013-01-01

    The generation of wavelengths above 3 μm by nonlinear processes in short silica photonic crystal fibers is investigated numerically. It was found that wavelengths in the 3–3.5 μm range may be generated quite efficiently in centimeter-long fiber pieces when pumping with femtosecond pulses in the 1.......55–2 μm range. Wavelengths in the range of 3.5–4 μm can in principle be generated, but these require shorter fiber lengths for efficient extraction. The results indicate that useful 3 μm sources may be fabricated with existing silica-based fiber technology....

  2. Stochastic radio interferometric positioning in the 2.4 GHz range

    OpenAIRE

    Dil, B. J.; Havinga, P.J.M.; Ko, Jeong Gil; Eriksson, Joakim; Tsiftes, Nicolas; Dawson-Haggerty, Stephen; Vasseur, Jean-Philippe; Durvy, Mathilde

    2011-01-01

    This paper presents a novel Radio Interferometric Positioning System (RIPS), which we call Stochastic RIPS (SRIPS). Although RIPS provides centimeter accuracy, it is still not widely adopted due to (1) the limited set of suitable radio platforms and (2) the relatively long measurement and calibration times. SRIPS overcomes these practical limitations by (1) omitting the calibration phase of the existing RIPS and by (2) applying a novel positioning algorithm. SRIPS exploits the phenomenon of t...

  3. 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...

  4. Radio Pulsars

    CERN Document Server

    Beskin, V S; Gwinn, C R; Tchekhovskoy, A

    2015-01-01

    Almost 50 years after radio pulsars were discovered in 1967, our understanding of these objects remains incomplete. On the one hand, within a few years it became clear that neutron star rotation gives rise to the extremely stable sequence of radio pulses, that the kinetic energy of rotation provides the reservoir of energy, and that electromagnetic fields are the braking mechanism. On the other hand, no consensus regarding the mechanism of coherent radio emission or the conversion of electromagnetic energy to particle energy yet exists. In this review, we report on three aspects of pulsar structure that have seen recent progress: the self-consistent theory of the magnetosphere of an oblique magnetic rotator; the location, geometry, and optics of radio emission; and evolution of the angle between spin and magnetic axes. These allow us to take the next step in understanding the physical nature of the pulsar activity.

  5. Ultra-low-power short-range radios

    CERN Document Server

    Chandrakasan, Anantha

    2015-01-01

    This book explores the design of ultra-low-power radio-frequency integrated circuits (RFICs), with communication distances ranging from a few centimeters to a few meters. Such radios have unique challenges compared to longer-range, higher-powered systems. As a result, many different applications are covered, ranging from body-area networks to transcutaneous implant communications and Internet-of-Things devices. A mix of introductory and cutting-edge design techniques and architectures which facilitate each of these applications are discussed in detail. Specifically, this book covers:.

  6. Constraints on photoevaporation models from (lack of) radio emission in the Corona Australis protoplanetary disks

    CERN Document Server

    Galván-Madrid, Roberto; Manara, Carlo Felice; Forbrich, Jan; Pascucci, Ilaria; Carrasco-González, Carlos; Goddi, Ciriaco; Hasegawa, Yasuhiro; Takami, Michihiro; Testi, Leonardo; .,

    2014-01-01

    Photoevaporation due to high-energy stellar photons is thought to be one of the main drivers of protoplanetary disk dispersal. The fully or partially ionized disk surface is expected to produce free-free continuum emission at centimeter (cm) wavelengths that can be routinely detected with interferometers such as the upgraded Very Large Array (VLA). We use deep (rms noise down to 8 $\\mu$Jy beam$^{-1}$ in the field of view center) 3.5 cm maps of the nearby (130 pc) Corona Australis (CrA) star formation (SF) region to constrain disk photoevaporation models. We find that the radio emission from disk sources in CrA is surprisingly faint. Only 3 out of 10 sources within the field of view are detected, with flux densities of order $10^2$ $\\mu$Jy. However, a significant fraction of their emission is non-thermal. Typical upper limits for non-detections are $3\\sigma\\sim 60~\\mu$Jy beam$^{-1}$. Assuming analytic expressions for the free-free emission from extreme-UV (EUV) irradiation, we derive stringent upper limits to ...

  7. Centimeter-scale synthesis of ultrathin layered MoO3 by van der Waals epitaxy

    OpenAIRE

    Molina-Mendoza, Aday J.; Lado, Jose Luis; Island, Joshua; Niño, Miguel Angel; Aballe, Lucía; Foerster, Michael; Bruno, Flavio Y; López-Moreno, Alejandro; Vaquero-Garzon, Luis; van der Zant, Herre S. J.; Rubio-Bollinger, Gabino; Agraït, Nicolas; Perez, Emilio; Fernandez-Rossier, Joaquin; Castellanos-Gomez, Andres

    2015-01-01

    We report on the large-scale synthesis of highly oriented ultrathin MoO3 layers using a simple and low-cost atmospheric pressure by van der Waals epitaxy growth on muscovite mica substrates. By this method we are able to synthetize high quality centimeter-scale MoO3 crystals with thicknesses ranging from 1.4 nm (two layers) up to a few nanometers. The crystals can be easily transferred to an arbitrary substrate (such as SiO2) by a deterministic transfer method and extensively characterized to...

  8. Radio-optical alignments in a low radio luminosity sample

    CERN Document Server

    Lacy, M; Wold, M; Rawlings, S; Lilje, P B; Lacy, Mark; Ridgway, Susan E; Wold, Margrethe; Rawlings, Steve; Lilje, Per B

    1999-01-01

    We present an optically-based study of the alignment between the radio axes and the optical major axes of eight z~0.7 radio galaxies in a 7C sample. The radio galaxies in this sample are ~20-times less radio luminous than 3C galaxies at the same redshift, and are significantly less radio-luminous than any other well-defined samples studied to date. Using Nordic Optical Telescope images taken in good seeing conditions at rest-frame wavelengths just longward of the 4000A break, we find a statistically significant alignment effect in the 7C sample. Furthermore, in two cases where the aligned components are well separated from the host we have been able to confirm spectroscopically that they are indeed at the same redshift as the radio galaxy. However, a quantitative analysis of the alignment in this sample and in a corresponding 3C sample from HST archival data indicates that the percentage of aligned flux may be lower and of smaller spatial scale in the 7C sample. Our study suggests that alignments on the 50-kp...

  9. A MULTI-WAVELENGTH INVESTIGATION OF RCW175: AN H II REGION HARBORING SPINNING DUST EMISSION

    Energy Technology Data Exchange (ETDEWEB)

    Tibbs, C. T.; Compiegne, M.; Carey, S. [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Paladini, R. [NASA Herschel Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Dickinson, C.; Davies, R. D.; Davis, R. J. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester M13 9PL (United Kingdom); Alves, M. I. R. [Institut d' Astrophysique Spatiale, Universite Paris Sud XI, Batiment 121, 91405 Orsay (France); Flagey, N. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91125 (United States); Shenoy, S. [Space Science Division, NASA Ames Research Center, M/S 245-6, Moffett Field, CA 94035 (United States); Noriega-Crespo, A. [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Casassus, S. [Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago (Chile); Molinari, S.; Elia, D.; Pestalozzi, M.; Schisano, E., E-mail: ctibbs@ipac.caltech.edu [INAF-Istituto Fisica Spazio Interplanetario, Via Fosso del Cavaliere 100, I-00133 Roma (Italy)

    2012-08-01

    Using infrared, radio continuum, and spectral observations, we performed a detailed investigation of the H II region RCW175. We determined that RCW175, which actually consists of two separate H II regions, G29.1-0.7 and G29.0-0.6, is located at a distance of 3.2 {+-} 0.2 kpc. Based on the observations we infer that the more compact G29.0-0.6 is less evolved than G29.1-0.7 and was possibly produced as a result of the expansion of G29.1-0.7 into the surrounding interstellar medium. We compute a star formation rate for RCW175 of (12.6 {+-} 1.9) Multiplication-Sign 10{sup -5} M{sub Sun} yr{sup -1}, and identified six possible young stellar object candidates within its vicinity. Additionally, we estimate that RCW175 contains a total dust mass of 215 {+-} 53 M{sub Sun }. RCW175 has previously been identified as a source of anomalous microwave emission (AME), an excess of emission at centimeter wavelengths often attributed to electric dipole radiation from the smallest dust grains. We find that the AME previously detected in RCW175 is not correlated with the smallest dust grains (polycyclic aromatic hydrocarbons or small carbonaceous dust grains), but rather with the exciting radiation field within the region. This is a similar result to that found in the Perseus molecular cloud, another region which harbors AME, suggesting that the radiation field may play a pivotal role in the production of this new Galactic emission mechanism. Finally, we suggest that these observations may hint at the importance of understanding the role played by the major gas ions in spinning dust models.

  10. VLBI detection of an Infrared-Faint Radio Source

    OpenAIRE

    Norris, Ray P.; Tingay, Steven; Phillips, Chris; Middelberg, Enno; Deller, Adam; Appleton, Philip N.

    2007-01-01

    Infrared-Faint Radio Sources represent a new and unexpected class of object which is bright at radio wavelengths but unusually faint at infrared wavelengths. If, like most mJy radio sources, they were either conventional active or star-forming galaxies in the local Universe, we would expect them to be detectable at infrared wavelengths, and so their non-detection by the Spitzer Space Telescope is surprising. Here we report the detection of one of these sources using Very Long Baseline Interfe...

  11. Workshop on Radio Transients

    Science.gov (United States)

    Croft, Steve; Gaensler, Bryan

    2012-04-01

    abstract-type="normal">SummaryWe are entering a new era in the study of variable and transient radio sources. This workshop discussed the instruments and the strategies employed to study those sources, how they are identified and classified, how results from different surveys can be compared, and how radio observations tie in with those at other wavelengths. The emphasis was on learning what common ground there is between the plethora of on-going projects, how methods and code can be shared, and how best practices regarding survey strategy could be adopted. The workshop featured the four topics below. Each topic commenced with a fairly brief introductory talk, which then developed into discussion. By way of preparation, participants had been invited to upload and discuss one slide per topic to a wiki ahead of the workshop. 1. Telescopes, instrumentation and survey strategy. New radio facilities and on-going projects (including upgrades) are both studying the variability of the radio sky, and searching for transients. The discussion first centred on the status of those facilities, and on projects with a time-domain focus, both ongoing and planned, before turning to factors driving choices of instrumentation, such as phased array versus single pixel feeds, the field of view, spatial and time resolution, frequency and bandwidth, depth, area, and cadence of the surveys. 2. Detection, pipelines, and classification. The workshop debated (a) the factors that influence decisions to study variability in the (u,v) plane, in images, or in catalogues, (b) whether, and how much, pipeline code could potentially be shared between one project and another, and which software packages are best for different approaches, (c) how data are stored and later accessed, and (d) how transients and variables are defined and classified. 3. Statistics, interpretation, and synthesis. It then discussed how (i) the choice of facility and strategy and (ii) detection and classification schemes

  12. RADIO SUPERNOVAE IN THE GREAT SURVEY ERA

    International Nuclear Information System (INIS)

    Radio properties of supernova outbursts remain poorly understood despite longstanding campaigns following events discovered at other wavelengths. After ∼30 years of observations, only ∼50 supernovae have been detected at radio wavelengths, none of which are Type Ia. Even the most radio-loud events are ∼104 fainter in the radio than in the optical; to date, such intrinsically dim objects have only been visible in the very local universe. The detection and study of radio supernovae (RSNe) will be fundamentally altered and dramatically improved as the next generation of radio telescopes comes online, including EVLA, ASKAP, and MeerKAT, and culminating in the Square Kilometer Array (SKA); the latter should be ∼> 50 times more sensitive than present facilities. SKA can repeatedly scan large (∼> 1 deg2) areas of the sky, and thus will discover RSNe and other transient sources in a new, automatic, untargeted, and unbiased way. We estimate that SKA will be able to detect core-collapse RSNe out to redshift z ∼ 5, with an all-redshift rate of ∼620 events yr-1 deg-2, assuming a survey sensitivity of 50 nJy and radio light curves like those of SN 1993J. Hence, SKA should provide a complete core-collapse RSN sample that is sufficient for statistical studies of radio properties of core-collapse supernovae. EVLA should find ∼160 events yr-1 deg-2 out to redshift z ∼ 3, and other SKA precursors should have similar detection rates. We also provided recommendations of the survey strategy to maximize the RSN detections of SKA. This new radio core-collapse supernova sample will complement the detections from the optical searches, such as the LSST, and together provide crucial information on massive star evolution, supernova physics, and the circumstellar medium, out to high redshift. Additionally, SKA may yield the first radio Type Ia detection via follow-up of nearby events discovered at other wavelengths.

  13. Infrared-Faint Radio Sources: A Cosmological View - AGN Number Counts, the Cosmic X-Ray Background and SMBH Formation

    OpenAIRE

    Zinn, Peter-Christian; Middelberg, Enno; Ibar, Edo

    2011-01-01

    Context. Infrared Faint Radio Sources (IFRS) are extragalactic emitters clearly detected at radio wavelengths but barely detected or undetected at optical and infrared wavelengths, with 5 sigma sensitivities as low as 1 uJy. Aims. Recent SED-modelling and analysis of their radio properties shows that IFRS are consistent with a population of (potentially extremely obscured) high-redshift AGN at 3

  14. 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

  15. Centimeter spatial resolution of distributed optical fiber sensor for structural health monitoring

    Science.gov (United States)

    Zou, Lufan; Bao, Xiaoyi; Wan, Yidun; Ravet, Fabien; Chen, Liang

    2004-11-01

    We present a sensing principle of the coherent probe-pump based Brillouin sensor (CPPBBS) that offers a new method to achieve centimeter spatial resolution with high frequency resolution. A combination of continuous wave (cw) and pulse source as the probe (Stokes) beam and cw laser as the pump beam have resulted in stronger Brillouin interaction of Stokes and pump inside the pulse-length in the form of cw-pump and pulse-pump interactions. We find that the coherent portion inside the pulse-length of these two interactions due to the same phase has a very high Brillouin amplification. The Brillouin profile originating from the coherent interaction of pulse-pump with cw-pump results in high temperature and strain accuracy with centimeter resolution, which allows us to detect 1.5 cm out-layer crack on an optical ground wire (OPGW) cable. The out-layer damaged regions on an optical ground wire (OPGW) cable have been identified successfully by measuring the strain distributions every 5 cm using this technology. The stress increased to 127 kN which corresponds to more than 7500 micro-strain in the fibers. The locations of structural indentations comprising repaired and undamaged regions are found and distinguished using their corresponding strain data. The elongation of repaired region increases with time on the stress of 127 kN. These results are quantified in terms of the fiber orientation, stress, and behavior relative to undamaged sections.

  16. Impact of surface imperfections on the Casimir force for lenses of centimeter-size curvature radii

    International Nuclear Information System (INIS)

    The impact of imperfections, which are always present on surfaces of lenses with centimeter-size curvature radii, on the Casimir force in the lens-plate geometry is investigated. It is shown that the commonly used formulation of the proximity force approximation is inapplicable for spherical lenses with surface imperfections, such as bubbles and pits. More general expressions for the Casimir force are derived that take surface imperfections into account. Using these expressions, we show that surface imperfections can both increase and decrease the magnitude of the Casimir force up to a few tens percent when compared with the case of a perfectly spherical lens. We demonstrate that the Casimir force between a perfectly spherical lens and a plate described by the Drude model can be made approximately equal to the force between a sphere with some surface imperfection and a plate described by the plasma model, and vice versa. In the case of a metallic sphere and a semiconductor plate, approximately the same Casimir forces are obtained for four different descriptions of charge carriers in the semiconductor if appropriate surface imperfections on the lens surface are present. The conclusion is made that there is a fundamental problem in the interpretation of measurement data for the Casimir force using spherical lenses of centimeter-size radii.

  17. Weak Lensing with Radio Continuum Surveys

    CERN Document Server

    Patel, Prina

    2016-01-01

    Weak gravitational lensing is a powerful probe of cosmology and has emerged as a key probe for the Dark Universe. Up till now this science has been conducted mainly at optical wavelengths. Current upgraded and future radio facilities will provide greatly improved data that will allow lensing measurements to be made at these longer wavelengths. In this proceedings I show how the larger facilities such as the SKA can produce game changing cosmological measurements even compared to future optical telescopes. I will also discuss how radio surveys can also provide unique ways in which some of the most problematic systematic errors can be mitigated through the extra information that can be provided in the form of polarisation and rotational velocity measurements. I will also demonstrate the advantages to having overlapping optical and radio weak lensing surveys and how their cross-correlation leads to a cleaner extraction of the cosmological information. Key to the realisation of the great promise of radio weak len...

  18. Three-Dimensional Statistics of Radio Polarimetry

    OpenAIRE

    McKinnon, Mark M.

    2003-01-01

    The measurement of radio polarization may be regarded as a three-dimensional statistical problem because the large photon densities at radio wavelengths allow the simultaneous detection of the three Stokes parameters which completely describe the radiation's polarization. The statistical nature of the problem arises from the fluctuating instrumental noise, and possibly from fluctuations in the radiation's polarization. A statistical model is used to derive the general, three-dimensional stati...

  19. Envelope Soliton in Solar Radio Emission

    Institute of Scientific and Technical Information of China (English)

    WANG De-Yu; Wangde; G. P. Chernov

    2000-01-01

    Several envelope soliton fine structures have been observed in solar radio metric-wave emission. We present amodel of 1ongitudinal modulational instability to explain these fine structures. It is found that this instability canonly occur in the condition of sound velocity being larger than Alfven velocity in corona. Therefore, the envelopesoliton fine structures should display in the coronal region with high temperature and low magnetic field, whichcorresponds to the solar radio emission in the region of meter and decameter wavelength.

  20. Amateur Planetary Radio Data Archived for Science and Education: Radio Jove

    Science.gov (United States)

    Thieman, J.; Cecconi, B.; Sky, J.; Garcia, L. N.; King, T. A.; Higgins, C. A.; Fung, S. F.

    2015-12-01

    The Radio Jove Project is a hands-on educational activity in which students, teachers, and the general public build simple radio telescopes, usually from a kit, to observe single frequency decameter wavelength radio emissions from Jupiter, the Sun, the galaxy, and the Earth usually with simple dipole antennas. Some of the amateur observers have upgraded their receivers to spectrographs and their antennas have become more sophisticated as well. The data records compare favorably to more sophisticated professional radio telescopes such as the Long Wavelength Array (LWA) and the Nancay Decametric Array. Since these data are often carefully calibrated and recorded around the clock in widely scattered locations they represent a valuable database useful not only to amateur radio astronomers but to the professional science community as well. Some interesting phenomena have been noted in the data that are of interest to the professionals familiar with such records. The continuous monitoring of radio emissions from Jupiter could serve as useful "ground truth" data during the coming Juno mission's radio observations of Jupiter. Radio Jove has long maintained an archive for thousands of Radio Jove observations, but the database was intended for use by the Radio Jove participants only. Now, increased scientific interest in the use of these data has resulted in several proposals to translate the data into a science community data format standard and store the data in professional archives. Progress is being made in translating Radio Jove data to the Common Data Format (CDF) and also in generating new observations in that format as well. Metadata describing the Radio Jove data would follow the Space Physics Archive Search and Extract (SPASE) standard. The proposed archive to be used for long term preservation would be the Planetary Data System (PDS). Data sharing would be achieved through the PDS and the Paris Astronomical Data Centre (PADC) and the Virtual Wave Observatory (VWO

  1. UWB Cognitive Radios

    OpenAIRE

    Kandeepan, Sithamparanathan; BALDINI Gianmarco; Piesiewicz, Radoslaw

    2011-01-01

    In this chapter we present UWB communication as a potential candidate for cognitive radio technology. Cognitive radios are intelligent radios that could adopt itself by sensing and learning the radio environment and optimize its transmission strategies to maximize the utilization of the scarce radio resources such as the radio spectrum. This has been motivated by the radio regulatory bodies around the world (EC, 2007; FCC, 2003) to utilize unused radio spectrum known as white s...

  2. Radio Variability of Radio Quiet and Radio Loud Quasars

    OpenAIRE

    Barvainis, Richard; Lehar, Joseph; Birkinshaw, Mark; Falke, Heino; Blundell, Katherine M.

    2004-01-01

    The majority of quasars are weak in their radio emission, with flux densities comparable to those in the optical, and energies far lower. A small fraction, about 10%, are hundreds to thousands of times stronger in the radio. Conventional wisdom holds that there are two classes of quasars, the radio quiets and radio louds, with a deficit of sources having intermediate power. Are there really two separate populations, and if so, is the physics of the radio emission fundamentally different betwe...

  3. VLBI detection of an Infrared-Faint Radio Source

    CERN Document Server

    Norris, Ray P; Phillips, Chris; Middelberg, Enno; Deller, Adam; Appleton, Philip N

    2007-01-01

    Infrared-Faint Radio Sources represent a new and unexpected class of object which is bright at radio wavelengths but unusually faint at infrared wavelengths. If, like most mJy radio sources, they were either conventional active or star-forming galaxies in the local Universe, we would expect them to be detectable at infrared wavelengths, and so their non-detection by the Spitzer Space Telescope is surprising. Here we report the detection of one of these sources using Very Long Baseline Interferometry, from which we conclude that the sources are driven by Active Galactic Nuclei. We suggest that these sources are either normal radio-loud quasars at high redshift or abnormally obscured radio galaxies.

  4. Speckles in interstellar radio-wave scattering

    Science.gov (United States)

    Desai, K. M.; Gwinn, C. R.; Reynolds, J.; King, E. A.; Jauncey, D.; Nicholson, G.; Flanagan, C.; Preston, R. A.; Jones, D. L.

    1991-01-01

    Observations of speckles in the scattering disk of the Vela pulsar are presented and speckle techniques for studying and circumventing scattering of radio waves by the turbulent interstellar plasma are discussed. The speckle pattern contains, in a hologrammatic fashion, complete information on the structure of the radio source as well as the distribution of the scattering material. Speckle observations of interstellar scattering of radio waves are difficult because of their characteristically short timescales and narrow bandwidths. Here, first observations are presented, taken at 13 cm wavelength with elements of the SHEVE VLBI network, of speckles in interstellar scattering.

  5. High-Tech 'Heart' of New-Generation Radio Telescope Passes First Test

    Science.gov (United States)

    2008-08-01

    process this torrent of data, the correlator will make 10 million billion calculations per second. Powerful, multi-antenna imaging radio-telescope systems use pairs of antennas as their basic building blocks. Each of the VLA's 27 giant dish antennas is combined electronically with every other antenna to form a multitude of pairs. Each pair contributes unique information that is used to build a highly-detailed image of some astronomical object. The successful two-antenna test thus verifies the design of the new correlator. "This achievement marks the first time that the complete chain of electronics for the EVLA has worked together, and represents a huge milestone in the project. Our congratulations go to our Canadian colleagues and to the NRAO staff members participating in this project. This is a job well done," said Fred Lo, Director of the National Radio Astronomy Observatory. The VLA Expansion, a ten-year project approved in 2001, is funded by 55 million from the United States National Science Foundation (NSF) and 1.75 million from the Mexican government. The Canadian correlator represents a contribution of about $17 million to the project. Throughout the project, the VLA has continued to operate, using a mix of the old and new-style antennas to provide an ongoing research tool. Over its lifetime, the VLA has been the most scientifically-productive ground-based telescope in the history of astronomy. When completed in 2012, the EVLA will be the most powerful centimeter-wavelength radio telescope in the world. The technology developed for the EVLA will enable progress on the next generation radio telescope called the Square Kilometer Array (SKA). The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. Plots of amplitude (top) and phase (bottom) from WIDAR correlator "first fringes" on August 7, 2008.

  6. Absolute brightness temperature measurements at 2.1-mm wavelength

    Science.gov (United States)

    Ulich, B. L.

    1974-01-01

    Absolute measurements of the brightness temperatures of the Sun, new Moon, Venus, Mars, Jupiter, Saturn, and Uranus, and of the flux density of DR21 at 2.1-mm wavelength are reported. Relative measurements at 3.5-mm wavelength are also preented which resolve the absolute calibration discrepancy between The University of Texas 16-ft radio telescope and the Aerospace Corporation 15-ft antenna. The use of the bright planets and DR21 as absolute calibration sources at millimeter wavelengths is discussed in the light of recent observations.

  7. Three-Dimensional Statistics of Radio Polarimetry

    CERN Document Server

    McKinnon, M M

    2003-01-01

    The measurement of radio polarization may be regarded as a three-dimensional statistical problem because the large photon densities at radio wavelengths allow the simultaneous detection of the three Stokes parameters which completely describe the radiation's polarization. The statistical nature of the problem arises from the fluctuating instrumental noise, and possibly from fluctuations in the radiation's polarization. A statistical model is used to derive the general, three-dimensional statistics that govern radio polarization measurements. The statistics are derived for specific cases of source-intrinsic polarization, with an emphasis on the orthogonal polarization modes in pulsar radio emission. The statistics are similar to those commonly found in other fields of the physical, biological, and Earth sciences. Given the highly variable linear and circular polarization of pulsar radio emission, an understanding of the three-dimensional statistics may be an essential prequisite to a thorough interpretation of...

  8. 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.

  9. Millisecond solar radio bursts in the metric wavelength range

    CERN Document Server

    Magdalenić, J; Zlobec, P; Vršnak, B; 10.1063/1.2347982

    2010-01-01

    A study and classification of super-short structures (SSSs) recorded during metric type IV bursts is presented. The most important property of SSSs is their duration, at half power ranging from 4-50 ms, what is up to 10 times shorter than spikes at corresponding frequencies. The solar origin of the SSSs is confirmed by one-to-one correspondence between spectral recordings of Artemis-IV1 and high time resolution single frequency measurements of the TSRS2. We have divided the SSSs in the following categories: 1. Broad-Band SSSs: They were partitioned in two subcategories, the SSS-Pulses and Drifting SSSs; 2. Narrow-band: They appear either as Spike-Like SSSs or as Patch-Like SSSs; 3. Complex SSS: They consist of the absorption-emission segments and were morphologically subdivided into Rain-drop Bursts (narrow-band emission head and a broad-band absorption tail) and Blinkers.

  10. 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

  11. Radio Observations of GRB Afterglows

    CERN Document Server

    Weiler, K W; Montes, M J; Weiler, Kurt W.; Panagia, Nino; Montes, Marcos J.

    2002-01-01

    Since 1997 the afterglow of gamma-ray bursting sources (GRBs) has occasionally been detected in the radio, as well in other wavelengths bands. In particular, the interesting and unusual gamma-ray burst GRB980425, thought to be related to the radio supernova SN1998bw, is a possible link between the two classes of objects. Analyzing the extensive radio emission data avaliable for SN1998bw, one can describe its time evolution within the well established framework available for the analysis of radio emission from supernovae. This then allows relatively detailed description of a number of physical properties of the object. The radio emission can best be explained as the interaction of a mildly relativistic shock with a dense preexplosion stellar wind-established circumstellar medium (CSM) that is highly structured both azimuthally, in clumps or filaments, and radially, with observed density enhancements. Because of its unusual characteristics for a Type Ib/c supernova, the relation of SN1998bw to GRB980425 is stre...

  12. Centimeter-deep tissue fluorescence microscopic imaging with high signal-to-noise ratio and picomole sensitivity

    CERN Document Server

    Cheng, Bingbing; Wei, Ming-Yuan; Pei, Yanbo; DSouza, Francis; Nguyen, Kytai T; Hong, Yi; Tang, Liping; Yuan, Baohong

    2015-01-01

    Fluorescence microscopic imaging in centimeter-deep tissue has been highly sought-after for many years because much interesting in vivo micro-information, such as microcirculation, tumor angiogenesis, and metastasis, may deeply locate in tissue. In this study, for the first time this goal has been achieved in 3-centimeter deep tissue with high signal-to-noise ratio (SNR) and picomole sensitivity under radiation safety thresholds. These results are demonstrated not only in tissue-mimic phantoms but also in actual tissues, such as porcine muscle, ex vivo mouse liver, ex vivo spleen, and in vivo mouse tissue. These results are achieved based on three unique technologies: excellent near infrared ultrasound-switchable fluorescence (USF) contrast agents, a sensitive USF imaging system, and an effective correlation method. Multiplex USF fluorescence imaging is also achieved. It is useful to simultaneously image multiple targets and observe their interactions. This work opens the door for future studies of centimeter...

  13. Multi-Wavelength Observations of Supernova Remnants

    Science.gov (United States)

    Williams, B.

    2012-01-01

    Supernova remnants (SNRs) provide a laboratory for studying various astrophysical processes, including particle acceleration, thermal and non thermal emission processes across the spectrum, distribution of heavy elements, the physics of strong shock waves, and the progenitor systems and environments of supernovae. Long studied in radio and X-rays, the past decade has seen a dramatic increase in the detection and subsequent study of SNRs in the infrared and gamma-ray regimes. Understanding the evolution of SNRs and their interaction with the interstellar medium requires a multi-wavelength approach. I will review the various physical processes observed in SNRs and how these processes are intertwined. In particular, I will focus on X-ray and infrared observations, which probe two very different but intrinsically connected phases of the ISM: gas and dust. I will discuss results from multi-wavelength studies of several SNRs at various stages of evolution, including Kepler, RCW 86, and the Cygnus Loop.

  14. 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.

  15. On the Superluminal Motion of Radio-Loud AGNs

    Indian Academy of Sciences (India)

    Zhi-Bin Zhang; Yi-Zhen Zhang

    2011-03-01

    Apparent superluminal motion of different radio-loud AGNs are similarly related with beaming effect. The cosmological expanding effect would play no part in the superluminal motion of radio galaxies, BL Lacertae objects as well as quasars.Meanwhile, we confirm that estimates for apparent velocity app and Doppler boosting factor based on multi-wavelength combination and variability are comparable.

  16. A widely tunable wavelength converter based on nonlinear polarization rotation in a carbon-nanotube-deposited D-shaped fiber.

    Science.gov (United States)

    Chow, K K; Yamashita, S; Song, Y W

    2009-04-27

    We demonstrate widely tunable wavelength conversion based on cross-phase modulation induced nonlinear polarization rotation in a carbon nanotubes (CNTs) deposited D-shaped fiber. A 5-centimeter-long CNT-deposited D-shaped fiber is used as the nonlinear medium for wavelength conversion of a 10 Gb/s non-return-to-zero signal. Wavelength tunable converted signal over 40 nm is obtained with around 2.5-dB power penalty in the bit-error-rate measurements. PMID:19399145

  17. Detection of SN1986j in NGC891 at millimetre wavelengths

    International Nuclear Information System (INIS)

    Supernova 1986j in NGC 891 has been detected at λ 1.2 mm and λ 3 mm at epoch 1986.8 using the IRAM 30-m millimetre radio telescope (MRT). It is the first supernova to be detected at near-millimetre wavelengths. The spectrum between λ3 and λ1.2 mm is flat, or rising towards shorter wavelengths, lying well above the extrapolation of the optically thin synchrotron radio spectrum of SN1986j at centimetre wavelengths at a similar epoch. The MRT observations are interpreted as arising from a pulsar-powered synchrotron nebula at the centre of the expanding layers of supernova ejecta which is physically distinct from the circumstellar interaction region from which the centimetre wavelength radio emission is produced. The observations suggest that millimetre wavelength and far-infrared spectrophotometry will be a useful tool to investigate pulsars and the pulsar environment in recent supernovae

  18. Tracing High Redshift Starformation in the Current and Next Generation of Radio Surveys

    CERN Document Server

    Seymour, Nick

    2009-01-01

    The current deepest radio surveys detect hundreds of sources per square degree below 0.1mJy. There is a growing consensus that a large fraction of these sources are dominated by star formation although the exact proportion has been debated in the literature. However, the low luminosity of these galaxies at most other wavelengths makes determining the nature of individual sources difficult. If future, deeper surveys performed with the next generation of radio instrumentation are to reap high scientific reward we need to develop reliable methods of distinguishing between radio emission powered by active galactic nuclei (AGN) and that powered by star formation. In particular, we believe that such discriminations should be based on purely radio, or relative to radio, diagnostics. These diagnostics include radio morphology, radio spectral index, polarisation, variability, radio luminosity and flux density ratios with non-radio wavelengths e.g. with different parts of the infrared (IR) regime. We discuss the advant...

  19. Wavelength conversion technology

    DEFF Research Database (Denmark)

    Stubkjær, Kristian

    1998-01-01

    Optical wavelength conversion is currently attracting much interest. This is because it enables full flexibility and eases management of WDM fibre networks. The tutorial will review existing and potential application areas. Examples of node architectures and network demonstrators that use wavelen...

  20. A New Radio Continuum Survey of the Sky at 1465 MHz between declinations -52 degrees and +68 degrees

    CERN Document Server

    Tello, C A S; Smoot, G F; Torres, S; Bersanelli, M

    2000-01-01

    We have mapped the total sky brightness at 1465 MHz in two adjacent 60-degree declination bands with the portable 5.5-m parabolic reflector of the Galactic Emission Mapping (GEM) project, an on-going international collaboration to survey the radio continuum of the sky in decimeter and centimeter wavelengths. The observations were conducted from two locations, one in the USA and the other in Brazil, using a novel instrumental approach to overcome the well-known shortcomings of survey experiments. Our strategy consists of a 1-rpm rotating dish to circularly scan the sky at 30 degrees from zenith. The dish uses a rim-halo to re-direct the spillover sidelobes of its backfire helical feed toward the sky and the entire assembly has been enclosed inside a wire mesh ground shield in order to minimize and level out the contamination from the ground. The diffraction characteristics of this set-up have been succesfully modelled and undesired systematic striping across the observed bands has been carefully removed by a b...

  1. Observations of Solar Radio Bursts with NRL LWA Antenna Prototypes

    Science.gov (United States)

    Stewart, K. P.; Hicks, B. C.; Crane, P. C.; Kassim, N. E.; MacDowall, R. J.; Bradley, R.; Erickson, W. C.

    2005-12-01

    We present spectra of solar bursts observed with active antenna prototypes. Combining active antenna systems developed for the NLTA (NRL Long-wavelength Test Array) and experience gained from BIRS (Bruny Island Radio Spectrometer) we have developed the GDRT (Goddard Decametric Radio Telescope). The GDRT and Green Bank Solar Radio Burst Spectrometer (GB/SRBS) serve as the northern hemisphere companions to BIRS, which operates in Tasmania. These instruments continuously scan from 100 MHz while simultaneously applying RFI mitigation algorithms to produce a continuous record of solar activity. This space weather initiative demonstrates one application of hardware developed for the LWA (Long Wavelength Array).

  2. The Radio Sky in the STARLAB

    Science.gov (United States)

    Fultz, C.; Smith, T.; Buck, S.; Harris, R.; Boltuch, D.; Hund, L.; Moffett, D.; Walsh, L.; LaFratta, M.; Castelaz, M. W.

    2005-12-01

    The STARLAB is a portable planetarium created, produced, and distributed by Learning Technologies, Ltd. Upon entering the STARLAB, images are projected onto the ceiling of the planetarium's dome using custom, interchangeable projection cylinders mounted on top of an ultrabright point light source. The STARLAB is ideal for teaching students about astronomy since it may be easily transported to schools across the nation. In order to take advantage of this powerful teaching tool, one of the foremost priorities of the Sensing the Radio Sky project was the development a projection cylinder that would visually interpret the quantitative data taken with radio telescopes and present that information in a form that students could understand and appreciate. The final version of the cylinder demonstrates a variety of topics relevant to an understanding of radio astronomy. When using the Radio Sky cylinder in the STARLAB, teachers may discuss the differences between optical and radio astronomy such as the structure of the Milky Way Galaxy, different sources of electromagnetic radiation, and important radio sources within and outside of the Galaxy. In addition, the flexibility of the cylinder's design allows for a variety of educational activities to be conducted within the STARLAB, all complemented by the Radio Sky cylinder's unique presentation of the Galaxy in radio wavelengths. We acknowledge support from the NSF Internship in Public Science Education Program grant number 0324729.

  3. Cosmic downsizing of powerful radio galaxies to low radio luminosities

    CERN Document Server

    Rigby, E E; Best, P N; Rosario, D; Röttgering, H J A

    2015-01-01

    At bright radio powers ($P_{\\rm 1.4 GHz} > 10^{25}$ W/Hz) the space density of the most powerful sources peaks at higher redshift than that of their weaker counterparts. This paper establishes whether this luminosity-dependent evolution persists for sources an order of magnitude fainter than those previously studied, by measuring the steep--spectrum radio luminosity function (RLF) across the range $10^{24} 10^{26}$ W/Hz the redshift of the peak space density increases with luminosity, whilst at lower radio luminosities the position of the peak remains constant within the uncertainties. This `cosmic downsizing' behaviour is found to be similar to that seen at optical wavelengths for quasars, and is interpreted as representing the transition from radiatively efficient to inefficient accretion modes in the steep-spectrum population. This conclusion is supported by constructing simple models for the space density evolution of these two different radio galaxy classes; these are able to successfully reproduce the ...

  4. Wavelength sweepable laser source

    DEFF Research Database (Denmark)

    2014-01-01

    Wavelength sweepable laser source is disclosed, wherein the laser source is a semiconductor laser source adapted for generating laser light at a lasing wavelength. The laser source comprises a substrate, a first reflector, and a second reflector. The first and second reflector together defines...... and having a rest position, the second reflector and suspension together defining a microelectromechanical MEMS oscillator. The MEMS oscillator has a resonance frequency and is adapted for oscillating the second reflector on either side of the rest position.; The laser source further comprises electrical...... connections adapted for applying an electric field to the MEMS oscillator. Furthermore, a laser source system and a method of use of the laser source are disclosed....

  5. Lithography-free centimeter-long nanochannel fabrication method using an electrospun nanofiber array

    International Nuclear Information System (INIS)

    Novel cost-effective methods for polymeric and metallic nanochannel fabrication have been demonstrated using an electrospun nanofiber array. Like other electrospun nanofiber-based nanofabrication methods, our system also showed high throughput as well as cost-effective performances. Unlike other systems, however, our fabrication scheme provides a pseudo-parallel nanofiber array a few centimeters long at a speed of several tens of fibers per second based on our unique inclined-gap fiber collecting system. Pseudo-parallel nanofiber arrays were used either directly for the PDMS molding process or for the metal lift-off process followed by the SiO2 deposition process to produce the nanochannel array. While the PDMS molding process was a simple fabrication based on one-step casting, the metal lift-off process followed by SiO2 deposition allowed finetuning on height and width of nanogrooves down to subhundred nanometers from a few micrometers. Nanogrooves were covered either with cover glass or with PDMS slab and nanochannel connectivity was investigated with a fluorescent dye. Also, nanochannel arrays were used to investigate mobility and conformations of λ-DNA. (paper)

  6. Centimeter-scale characterization of biogeochemical gradients at a wetland-aquifer interface using capillary electrophoresis

    Science.gov (United States)

    Baez-Cazull, S.; McGuire, J.T.; Cozzarelli, I.M.; Raymond, A.; Welsh, L.

    2007-01-01

    Steep biogeochemical gradients were measured at mixing interfaces in a wetland-aquifer system impacted by landfill leachate in Norman, Oklahoma. The system lies within a reworked alluvial plain and is characterized by layered low hydraulic conductivity wetland sediments interbedded with sandy aquifer material. Using cm-scale passive diffusion samplers, "peepers", water samples were collected in a depth profile to span interfaces between surface water and a sequence of deeper sedimentary layers. Geochemical indicators including electron acceptors, low-molecular-weight organic acids, base cations, and NH4+ were analyzed by capillary electrophoresis (CE) and field techniques to maximize the small sample volumes available from the centimeter-scale peepers. Steep concentration gradients of biogeochemical indicators were observed at various interfaces including those created at sedimentary boundaries and boundaries created by heterogeneities in organic C and available electron acceptors. At the sediment-water interface, chemical profiles with depth suggest that SO42 - and Fe reduction dominate driven by inputs of organic C from the wetland and availability of electron acceptors. Deeper in the sediments (not associated with a lithologic boundary), a steep gradient of organic acids (acetate maximum 8.8 mM) and NH4+ (maximum 36 mM) is observed due to a localized source of organic matter coupled with the lack of electron acceptor inputs. These findings highlight the importance of quantifying the redox reactions occurring in small interface zones and assessing their role on biogeochemical cycling at the system scale. ?? 2007 Elsevier Ltd. All rights reserved.

  7. Surface Engineering of Copper Foils for Growing Centimeter-Sized Single-Crystalline Graphene.

    Science.gov (United States)

    Lin, Li; Li, Jiayu; Ren, Huaying; Koh, Ai Leen; Kang, Ning; Peng, Hailin; Xu, H Q; Liu, Zhongfan

    2016-02-23

    The controlled growth of high-quality graphene on a large scale is of central importance for applications in electronics and optoelectronics. To minimize the adverse impacts of grain boundaries in large-area polycrystalline graphene, the synthesis of large single crystals of monolayer graphene is one of the key challenges for graphene production. Here, we develop a facile surface-engineering method to grow large single-crystalline monolayer graphene by the passivation of the active sites and the control of graphene nucleation on copper surface using the melamine pretreatment. Centimeter-sized hexagonal single-crystal graphene domains were successfully grown, which exhibit ultrahigh carrier mobilities exceeding 25,000 cm(2) V(-1) s(-1) and quantum Hall effects on SiO2 substrates. The underlying mechanism of melamine pretreatments were systematically investigated through elemental analyses of copper surface in the growth process of large single-crystals. This present work provides a surface design of a catalytic substrate for the controlled growth of large-area graphene single crystals. PMID:26832229

  8. Ultraviolet and radio flares from UX Arietis and HR 1099

    Science.gov (United States)

    Lang, Kenneth R.; Willson, Robert F.

    1988-01-01

    Simultaneous observations of the RS CVn systems UX Ari and HR 1099 with the IUE satellite and the VLA are presented. Flaring activity is observed at ultraviolet wavelengths with the IUE when none is detected at radio wavelengths with the VLA. Radio flares with no detectable ultraviolet activity have also been observed. Thus, flares in the two spectral regions are either uncorrelated or weakly correlated. The flaring emission probably originates in different regions at the two wavelengths. Radio flares from RS CVn stars may originate in sources that are larger than, or comparable to, a star in size. This is in sharp contrast to compact, coherent radio flares from dwarf M stars. The ultraviolet flares from RS CVn stars probably originate in sources that are smaller than a component star.

  9. Observational Analysis of the Phases in Solar Flare Occurred Radio Fast Fine Structures%射电快速精细结构在太阳耀斑中产生相位的观测分析

    Institute of Scientific and Technical Information of China (English)

    谢瑞祥; 汪敏

    2001-01-01

    The statistical analysis of 40 solar radio events which were obtained with Radio Synchronous Observation System at four frequencies(1.42, 2.13, 2.84, and 4.26 GHz) in Yunnan Observatory during December 1989 to January 1994 and the spectrometer(2.6~3.8GHz) in Beijing Observatory during November 1996 to May 1998 is made in this paper.The phase of the radio FFS occurred at low frequency band of microwave(long centimeter to short decimeter wavelengths)in flare is approached.The regularity of the phase of flare occurred radio FFS in this frequency range is found.%利用云南天文台射电四频率(1.42, 2.13, 2.84和4.26GHz)同步观测系统于1989.12~1994.1和北京天文台射电频谱仪(2.6~3.8GHz)于1996.11~1998.5的观测资料,仅对太阳和射电爆发中40个事件作了一个初步的统计分析,就微波低频段的快速精细结构在耀斑中产生的相位作了一个探索,期望找出太阳射电在此频段内快速活动产生相位的规律性。

  10. Radios Online

    OpenAIRE

    Vázquez Zapata, Guillermo

    2013-01-01

    Dissertação apresentada à Universidade Fernando Pessoa como parte dos requisitos para a obtenção do grau de mestre em Ciências da Comunicação, especialização em Jornalismo A través de este trabajo se investiga la forma en la que el fenómeno de la tecnología online influye en un medio de origen tradicional como es la radio y las consecuencias de una transición mediática sin precedentes. Realizando una visión histórica y analítica del desarrollo tecnológico en relación con los me...

  11. Radio emission from radio-quiet quasars

    International Nuclear Information System (INIS)

    The results of a search for radio emission from bright, optically selected quasars at 5 GHz are reported. The work was initiated to examine the distribution of radio - to -optical luminosity ratios and also, by optical and IR photometry, to seek correlations between IR - optical properties and radio emission. It is shown that quasars of bright apparent magnitude exhibit a significantly higher incidence of radio emission than would be expected on the basis of a scaling of detection thresholds. (UK)

  12. Radio and optical realizations of celestial reference frames

    CERN Document Server

    Lambert, S B; Le Poncin-Lafitte, C; Barache, C; Souchay, J

    2006-01-01

    The International Celestial Reference Frame (ICRF, Ma et al. 1998) is currently the best realization of a quasi-inertial reference system. It is based on more than 10 years of cumulated geodetic and astrometric VLBI observations of compact extragalactic objects at centimetric wavelengths. In the perspective of the realization of an accurate optical counterpart of the ICRF using future space astrometry missions like GAIA or SIM, this paper investigates the consistency of celestial reference frames realized through the same subset of compact extragalactic radio sources at optical wavelengths. Celestial reference frames realized in radio wavelengths with the VLBA Calibrator Survey (VCS) data and in optical wavelengths with the Sloan Digital Sky Survey (SDSS) data (DR3 quasar catalogue and DR5) are compared in terms of radio-optical distances between the common sources, global rotation of the axes and offset of the equator.

  13. Detecting the cosmic web with radio surveys

    CERN Document Server

    Vazza, F; Gheller, C; Ferrari, C; Bonafede, A

    2016-01-01

    We study the challenges to detect the cosmic web at radio wavelengths with state-of-the-art cosmological simulations of extragalactic magnetic fields. The incoming generation of radio surveys operating at low frequency, like LOFAR, SKA-LOW and MWA will have the best chance to detect the large-scale, low surface brightness emission from the shocked cosmic web. The detected radio emission will enable to constrain the average magnetisation level of the gas in filaments and the acceleration efficiency of electrons by strong shocks. In case of detections, through statistical modelling (e.g. correlation functions) it will be possible to discriminate among competing scenarios for the magnetisation of large-scale structures (i.e. astrophysical versus primordial scenarios), making radio surveys an important probe of cosmic magnetogenesis.

  14. Where the active galaxies live: a panchromatic view of radio-AGN in the AKARI-NEP field

    CERN Document Server

    Karouzos, Marios; Trichas, Markos

    2013-01-01

    We study the host galaxy properties of radio sources in the AKARI-North Ecliptic Pole (NEP) field, using an ensemble of multi-wavelength datasets. We identify both radio-loud and radio-quiet AGN and study their host galaxy properties by means of SED fitting. We investigate the relative importance of nuclear and star-formation activity in radio-AGN and assess the role of radio-AGN as efficient quenchers of star-formation in their host galaxies.

  15. Strictly Transparent Wavelength Conversion Using Multi-Wavelength Signal Generation

    Institute of Scientific and Technical Information of China (English)

    Eiichi; Yamada; Hiroaki; Sanjoh; Yuzo; Yoshikuni

    2003-01-01

    We succeeded in strictly transparent wavelength conversion by means of channel selection from multi-wavelength signals generated by sinusoidal modulation of input signal. Modulation-format-independent and bit-rate-independent wavelength conversion is achieved with small power penalty.

  16. Kiloparsec-scale Radio Structures in Narrow-line Seyfert 1 Galaxies

    CERN Document Server

    Doi, Akihiro; Kawakatu, Nozomu; Kino, Motoki; Nagai, Hiroshi; Asada, Keiichi

    2012-01-01

    We report the finding of kiloparsec (kpc)-scale radio structures in three radio-loud narrow-line Seyfert 1 (NLS1) galaxies from the Faint Images of the Radio Sky at Twenty-centimeters (FIRST) of the Very Large Array (VLA), which increases the number of known radio-loud NLS1s with kpc-scale structures to six, including two gamma-ray emitting NLS1s (PMN J0948+0022 and 1H 0323+342) detected by the Fermi Gamma-ray Space Telescope. The detection rate of extended radio emissions in NLS1s is lower than that in broad-line active galactic nuclei (AGNs) with a statistical significance. We found both core-dominated (blazar-like) and lobe-dominated (radio-galaxy-like) radio structures in these six NLS1s, which can be understood in the framework of the unified scheme of radio-loud AGNs that considers radio galaxies as non-beamed parent populations of blazars. Five of the six NLS1s have (i) extended radio luminosities suggesting jet kinetic powers of >~10^44 erg/s, which is sufficient to make jets escape from hosts' dense ...

  17. How to Identify and Separate Bright Galaxy Clusters from the Low-frequency Radio Sky?

    OpenAIRE

    Wang, Jingying; Xu, Haiguang; Gu, Junhua; An, Tao; Cui, Haijuan; Li, Jianxun; Zhang, Zhongli; Zheng, Qian; Wu, Xiang-Ping

    2010-01-01

    In this work we simulate the $50-200$ MHz radio sky that is constrained in the field of view ($5^{\\circ}$ radius) of the 21 Centimeter Array (21CMA), by carrying out Monte-Carlo simulations to model redshifted cosmological reionization signals and strong contaminating foregrounds, including emissions from our Galaxy, galaxy clusters, and extragalactic point sources. As an improvement of previous works, we consider in detail not only random variations of morphological and spectroscopic paramet...

  18. SMC SMP 24: A Newly Radio-Detected Planetary Nebula in the Small Magellanic Cloud

    Directory of Open Access Journals (Sweden)

    Bojicic, I. S.

    2010-12-01

    Full Text Available In this paper we report a new radio-continuum detection of an extragalactic planetary nebula (PN: SMC~SMP~24. We show the radio-continuum image of this PN and present the measured radio data. The newly reduced radio observations are consistent with the multi-wavelength data and derived parameters found in the literature. SMC~SMP~24 appears to be a young and compact PN, optically thick at frequencies below 2~GHz.

  19. Free-space wavelength-multiplexed optical scanner demonstration.

    Science.gov (United States)

    Yaqoob, Zahid; Riza, Nabeel A

    2002-09-10

    Experimental demonstration of a no-moving-parts free-space wavelength-multiplexed optical scanner (W-MOS) is presented. With fast tunable lasers or optical filters and planar wavelength dispersive elements such as diffraction gratings, this microsecond-speed scanner enables large several-centimeter apertures for subdegree angular scans. The proposed W-MOS design incorporates a unique optical amplifier and variable optical attenuator combination that enables the calibration and modulation of the scanner response, leading to any desired scanned laser beam power shaping. The experimental setup uses a tunable laser centered at 1560 nm and a 600-grooves/mm blazed reflection grating to accomplish an angular scan of 12.92 degrees as the source is tuned over an 80-nm bandwidth. The values for calculated maximum optical beam divergance, required wavelength resolution, beam-pointing accuracy, and measured scanner insertion loss are 1.076 mrad, 0.172 nm, 0.06 mrad, and 4.88 dB, respectively. PMID:12224780

  20. Analysis, Design and Fabrication of centimeter-wave Dielectric Fresnel Zone Plate Lens and reflector

    OpenAIRE

    Mahmoudi, Ali; Azalzadeh, Reza

    2007-01-01

    Fresnel lens has a long history in optics. This concept at non-optical wavelengths is also applicable. In this paper we report design and fabrication of a half and quarter wave dielectric Fresnel lens made of Plexiglas, and a Fresnel reflector at 11.1 GHz frequency. We made two lenses and one reflector at same frequency and compare their gain and radiation pattern to simulated results. Some methods for better focusing action will be introduced.

  1. Analysis, Design and Fabrication of centimeter-wave Dielectric Fresnel Zone Plate Lens and reflector

    CERN Document Server

    Mahmoudi, A; Mahmoudi, Ali; Azalzadeh, Reza

    2005-01-01

    Fresnel lens has a long history in optics. This concept at non-optical wavelengths is also applicable. In this paper we report design and fabrication of a half and quarter wave dielectric Fresnel lens made of Plexiglas, and a Fresnel reflector at 11.1 GHz frequency. We made two lenses and one reflector at same frequency and compare their gain and radiation pattern to simulated results. Some methods for better focusing action will be introduced.

  2. Distributed fiber Brillouin strain and temperature sensor with centimeter spatial resolution by coherent probe-pump technique

    Science.gov (United States)

    Zou, Lufan; Bao, Xiaoyi; Wan, Yidun; Ravet, Fabien; Chen, Liang

    2005-05-01

    We present a sensing principle of the distributed fiber Brillouin strain and temperature sensor by coherent probe-pump technique that offers a new method to achieve centimeter spatial resolution with high frequency resolution. A combination of continuous wave (cw) and pulse source as the probe (Stokes) beam and cw laser as the pump beam have resulted in stronger Brillouin interaction of Stokes and pump inside the pulse-length in the form of cw-pump and pulse-pump interactions. We find that the coherent portion inside the pulse-length of these two interactions due to the same phase has a very high Brillouin amplification. The Brillouin profile originating from the coherent interaction of pulse-pump with cw-pump results in high temperature and strain accuracy with centimeter resolution, which has been verified by successfully detecting 1.5 cm out-layer crack on an optical ground wire (OPGW) cable.

  3. Accelerating Into the Future: From 0 to GeV in a Few Centimeters (LBNL Summer Lecture Series)

    International Nuclear Information System (INIS)

    Summer Lecture Series 2008: By exciting electric fields in plasma-based waveguides, lasers accelerate electrons in a fraction of the distance conventional accelerators require. The Accelerator and Fusion Research Division's LOASIS program, headed by Wim Leemans, has used 40-trillion-watt laser pulses to deliver billion-electron-volt (1 GeV) electron beams within centimeters. Leemans looks ahead to BELLA, 10-GeV accelerating modules that could power a future linear collider.

  4. Accelerating Into the Future: From 0 to GeV in a Few Centimeters (LBNL Summer Lecture Series)

    Energy Technology Data Exchange (ETDEWEB)

    Leemans, Wim [LOASIS Program, AFRD

    2008-07-08

    Summer Lecture Series 2008: By exciting electric fields in plasma-based waveguides, lasers accelerate electrons in a fraction of the distance conventional accelerators require. The Accelerator and Fusion Research Division's LOASIS program, headed by Wim Leemans, has used 40-trillion-watt laser pulses to deliver billion-electron-volt (1 GeV) electron beams within centimeters. Leemans looks ahead to BELLA, 10-GeV accelerating modules that could power a future linear collider.

  5. Matching Radio Catalogs with Realistic Geometry: Application to SWIRE and ATLAS

    CERN Document Server

    Fan, Dongwei; Norris, Ray P; Hopkins, Andrew M

    2015-01-01

    Crossmatching catalogs at different wavelengths is a difficult problem in astronomy, especially when the objects are not point-like. At radio wavelengths an object can have several components corresponding, for example, to a core and lobes. {Considering not all radio detections correspond to visible or infrared sources, matching these catalogs can be challenging.} Traditionally this is done by eye for better quality, which does not scale to the large data volumes expected from the next-generation of radio telescopes. We present a novel automated procedure, using Bayesian hypothesis testing, to achieve reliable associations by explicit modelling of a particular class of radio-source morphology. {The new algorithm not only assesses the likelihood of an association between data at two different wavelengths, but also tries to assess whether different radio sources are physically associated, are double-lobed radio galaxies, or just distinct nearby objects.} Application to the SWIRE and ATLAS CDF-S catalogs shows t...

  6. 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...

  7. A measurement of the brightness temperature of Saturn's rings at 8-mm wavelength

    Science.gov (United States)

    Janssen, M. A.; Olsen, E. T.

    1978-01-01

    The brightness temperature of Saturn's rings has been measured at 8-mm wavelength using a millimeter-wavelength interferometer. A ring brightness temperature of 12.7 + or -2 K is obtained with the assumption that the rings are of uniform brightness and the region of emission coincides with the visible A and B rings. This result is higher than comparable results obtained at centimeter wavelengths and may indicate a small increase in the thermal emission from the rings at 8 mm. The low brightness temperature places significant constraints on the nature of the ring particles and implies that they must be either highly metallic or of limited size and composed of a low-loss dielectric material such as water ice.

  8. Quadrature wavelength scanning interferometry.

    Science.gov (United States)

    Moschetti, Giuseppe; Forbes, Alistair; Leach, Richard K; Jiang, Xiang; O'Connor, Daniel

    2016-07-10

    A novel method to double the measurement range of wavelength scanning interferometery (WSI) is described. In WSI the measured optical path difference (OPD) is affected by a sign ambiguity, that is, from an interference signal it is not possible to distinguish whether the OPD is positive or negative. The sign ambiguity can be resolved by measuring an interference signal in quadrature. A method to obtain a quadrature interference signal for WSI is described, and a theoretical analysis of the advantages is reported. Simulations of the advantages of the technique and of signal errors due to nonideal quadrature are discussed. The analysis and simulation are supported by experimental measurements to show the improved performances. PMID:27409307

  9. Modeling of LEO Orbital Debris Populations in Centimeter and Millimeter Size Regimes

    Science.gov (United States)

    Xu, Y.-L.; Hill, . M.; Horstman, M.; Krisko, P. H.; Liou, J.-C.; Matney, M.; Stansbery, E. G.

    2010-01-01

    The building of the NASA Orbital Debris Engineering Model, whether ORDEM2000 or its recently updated version ORDEM2010, uses as its foundation a number of model debris populations, each truncated at a minimum object-size ranging from 10 micron to 1 m. This paper discusses the development of the ORDEM2010 model debris populations in LEO (low Earth orbit), focusing on centimeter (smaller than 10 cm) and millimeter size regimes. Primary data sets used in the statistical derivation of the cm- and mm-size model populations are from the Haystack radar operated in a staring mode. Unlike cataloged objects of sizes greater than approximately 10 cm, ground-based radars monitor smaller-size debris only in a statistical manner instead of tracking every piece. The mono-static Haystack radar can detect debris as small as approximately 5 mm at moderate LEO altitudes. Estimation of millimeter debris populations (for objects smaller than approximately 6 mm) rests largely on Goldstone radar measurements. The bi-static Goldstone radar can detect 2- to 3-mm objects. The modeling of the cm- and mm-debris populations follows the general approach to developing other ORDEM2010-required model populations for various components and types of debris. It relies on appropriate reference populations to provide necessary prior information on the orbital structures and other important characteristics of the debris objects. NASA's LEO-to-GEO Environment Debris (LEGEND) model is capable of furnishing such reference populations in the desired size range. A Bayesian statistical inference process, commonly adopted in ORDEM2010 model-population derivations, changes a priori distribution into a posteriori distribution and thus refines the reference populations in terms of data. This paper describes key elements and major steps in the statistical derivations of the cm- and mm-size debris populations and presents results. Due to lack of data for near 1-mm sizes, the model populations of 1- to 3.16-mm

  10. Radio frequency detection assembly and method for detecting radio frequencies

    Science.gov (United States)

    Cown, Steven H.; Derr, Kurt Warren

    2010-03-16

    A radio frequency detection assembly is described and which includes a radio frequency detector which detects a radio frequency emission produced by a radio frequency emitter from a given location which is remote relative to the radio frequency detector; a location assembly electrically coupled with the radio frequency detector and which is operable to estimate the location of the radio frequency emitter from the radio frequency emission which has been received; and a radio frequency transmitter electrically coupled with the radio frequency detector and the location assembly, and which transmits a radio frequency signal which reports the presence of the radio frequency emitter.

  11. Study of meter wavelength continuum radiation from the Sun

    International Nuclear Information System (INIS)

    Solar continuum radiation at metric wavelengths occurs in a wide variety of forms. It can have a lifetime ranging from less than a minute to several weeks, a brightness temperature from near the quiet sun level to 1012 K and a degree of circular polarization from 0 to 100 percent. The three types of continuum radio bursts most closely related to the flare event are studied: Type V, flare continuum and moving Type IV. The principal objective is to understand the dynamics of the radio events, the radio emission mechanism and the physical properties of the corona. Synchrotron and Langmuir wave emission processes under coronal conditions are studied. The radiation from several electron energy distributions and from isotropic and anisotropic pitch angle distributions is calculated numerically. The results of these investigations are applied in deriving theoretical models of each type of continuum event

  12. Impact of cognitive radio on radio astronomy

    OpenAIRE

    Bentum, M. J.; Boonstra, A. J.; Baan, W. A.

    2010-01-01

    The introduction of new communication techniques requires an increase in the efficiency of spectrum usage. Cognitive radio is one of the new techniques that fosters spectrum efficiency by using unoccupied frequency spectrum for communications. However, cognitive radio will increase the transmission power density and cause an increasing level of Radio Frequency Interference (RFI), which may impact other services and particularly passive users of the spectrum. In this paper we present the princ...

  13. Very long baseline interferometry detection of an Infrared-Faint Radio Source

    OpenAIRE

    Norris, Ray P.; Tingay, Steven; Phillips, Chris; Middelberg, Enno; Deller, Adam; Appleton, Philip N.

    2007-01-01

    Infrared-Faint Radio Sources represent a new and unexpected class of object which is bright at radio wavelengths but unusually faint at infrared wavelengths. If, like most mJy radio sources, they were either conventional active or star-forming galaxies in the local Universe, we would expect them to be detectable at infrared wavelengths, and so their non-detection by the Spitzer Space Telescope is surprising. Here, we report the detection of one of these sources using very long baseline interf...

  14. OLFAR: the orbiting low frequency array, how a cube sat swarm becomes a novel radio astronomy instrument in space

    NARCIS (Netherlands)

    Bentum, Mark; Meijerink, Arjan; Boonstra, Albert-Jan; Verhoeven, Chris; Veen, van der Alle-Jan

    2010-01-01

    To study the physical processes in the Universe, observations are done at various wavelengths, from Gamma rays to optical and radio frequencies. At this moment research at low frequencies is one of the major topics in radio astronomy. Several Earth-based radio telescopes are being built and will be

  15. Wavelength-conserving grating router for intermediate wavelength density

    Science.gov (United States)

    Deri, Robert J.; Patel, Rajesh R.; Bond, Steven W.; Bennett, Cory V.

    2007-03-20

    A wavelength router to be used for fiber optical networking router is based on a diffraction grating which utilizes only N wavelengths to interconnect N inputs to N outputs. The basic approach is to augment the grating with additional couplers or wavelength selective elements so than N-1 of the 2N-1 outputs are combined with other N outputs (leaving only N outputs). One embodiment uses directional couplers as combiners. Another embodiment uses wavelength-selective couplers. Another embodiment uses a pair of diffraction gratings to maintain parallel propagation of all optical beams. Also, beam combining can be implemented either by using retroflection back through the grating pair or by using couplers.

  16. Data Reduction of Multi-wavelength Observations

    CERN Document Server

    Pilia, M; Pellizzoni, A P; Bachetti, M; Piano, G; Poddighe, A; Egron, E; Iacolina, M N; Melis, A; Concu, R; Possenti, A; Perrodin, D

    2015-01-01

    Multi-messenger astronomy is becoming the key to understanding the Universe from a comprehensive perspective. In most cases, the data and the technology are already in place, therefore it is important to provide an easily-accessible package that combines datasets from multiple telescopes at different wavelengths. In order to achieve this, we are working to produce a data analysis pipeline that allows the data reduction from different instruments without needing detailed knowledge of each observation. Ideally, the specifics of each observation are automatically dealt with, while the necessary information on how to handle the data in each case is provided by a tutorial that is included in the program. We first focus our project on the study of pulsars and their wind nebulae (PWNe) at radio and gamma-ray frequencies. In this way, we aim to combine time-domain and imaging datasets at two extremes of the electromagnetic spectrum. In addition, the emission has the same non-thermal origin in pulsars at radio and gam...

  17. GLAST Science Across Wavelengths

    Science.gov (United States)

    Blandford, R. D.

    2006-12-01

    The GLAST satellites is almost guaranteed to revolutionize GeV gamma ray astronomy because of the great discoveries that are being made at hard X-ray energy by the Suzaku and Swift satellites and in the TeV range using the H.E.S.S. and Magic telescopes. Unidentified EGRET sources are likely to be identified and new and fainter sources will be found. Known classes of sources blazars, pulsars, gamma ray bursts, supernova remnants, binary X-ray sources and so on will be monitored in much greater detail. Finally, there is the need to limit or even detect dark matter through its annihilation signature. The science that will emerge from GLAST will be determined in large measure by the effort that is put into multiwavelength observing. This will require significant commitments of observing time for monitoring pulsar arrival times, measuring faint galaxy spectra, detecting GeV gamma rays gamma ray bursts and so on. In this talk I will attempt to summarize current thinking on the GLAST multi-wavelength observing program and propose some new approaches.

  18. Laser system with wavelength converter

    DEFF Research Database (Denmark)

    2012-01-01

    The present invention relates to an apparatus comprising a diode laser (10) providing radiation in a first wavelength interval, a radiation conversion unit (12) having an input and an output, the radiation converter configured to receive the radiation in the first wavelength interval from the diode...... laser at the input, the radiation conversion unit configured to convert the radiation in the first wavelength interval to radiation in a second wavelength interval and the output configured to output the converted radiation, the second wavelength interval having one end point outside the first...... wavelength interval. Further, the invention relates to a method of optically pumping a target laser (14) in a laser system, the laser system comprising a laser source providing radiation at a first frequency, the laser source being optically connected to an input of a frequency converter, the frequency...

  19. Wavelength conversion devices and techniques

    DEFF Research Database (Denmark)

    Stubkjær, Kristian; Jørgensen, Carsten; Danielsen, Søren Lykke;

    1996-01-01

    Wavelength division multiplexed (WDM) networks are currently subject to an immense interest because of the extra capacity and flexibility they provide together with the possibilities for graceful system upgrades. For full network flexibility it is very attractive to be able to translate the chann...... wavelengths in an easy way and preferably without opto-electronic conversion. Here, we will first briefly look at advantages of employing optical wavelength converters in WDM networks and next review the optical wavelength conversion devices with emphasis on recent developments....

  20. Impact of cognitive radio on radio astronomy

    NARCIS (Netherlands)

    Bentum, M.J.; Boonstra, A.J.; Baan, W.A.

    2010-01-01

    The introduction of new communication techniques requires an increase in the efficiency of spectrum usage. Cognitive radio is one of the new techniques that fosters spectrum efficiency by using unoccupied frequency spectrum for communications. However, cognitive radio will increase the transmission

  1. Resonance and Radio

    Science.gov (United States)

    Starrett, Malin J.

    2008-01-01

    The science and technology of radio receives little attention in contemporary education. This article discusses ways to explore the basic operating principles of radio. (Contains 4 figures, 3 footnotes, and 2 notes.)

  2. DEEP SPITZER OBSERVATIONS OF INFRARED-FAINT RADIO SOURCES: HIGH-REDSHIFT RADIO-LOUD ACTIVE GALACTIC NUCLEI?

    International Nuclear Information System (INIS)

    Infrared-faint radio sources (IFRSs) are a rare class of objects which are relatively bright at radio wavelengths but very faint at infrared and optical wavelengths. Here we present sensitive near-infrared observations of a sample of these sources taken as part of the Spitzer Extragalactic Representative Volume Survey. Nearly all the IFRSs are undetected at a level of ∼1 μJy in these new deep observations, and even the detections are consistent with confusion with unrelated galaxies. A stacked image implies that the median flux density is S3.6μm ∼ 0.2 μJy or less, giving extreme values of the radio-infrared flux density ratio. Comparison of these objects with known classes of object suggests that the majority are probably high-redshift radio-loud galaxies, possibly suffering from significant dust extinction.

  3. The significance of radio astronomy for space research

    International Nuclear Information System (INIS)

    The age of radio astronomy started in the thirties with the discovery of radio emissions at a wavelength of 16.7 m from the milky way by the American Scientist Jansky. The first surprizing results however have been obtained with improved techniques not until world war II. With the large telescope in Jodrell Bank, English scientists discovered the 21 cm spectral line of neutral atomic hydrogen in 1951. (orig.)

  4. Performance Evaluation of Wavelength Routed Optical Network with Wavelength Conversion

    CERN Document Server

    Gond, Vitthal J

    2010-01-01

    The rapid development of telecommunication networks is driven by user demands for new applications and advances in technologies. The explosive growth of the internet traffic is due to its use for collecting the information, communication, multimedia application, entertainment, etc. These applications are imposing a tremendous demand for bandwidth capacity on telecommunication network. The introduction of fiber optics had proved to meet the huge demand of bandwidth. These requirement can be meet by all optical network which is capable of transmitting enormous data at very high speed, around 50 Tera bits per seconds (Tbps) A wavelength conversion technique is addressed in this paper to reduced the blocking probability in wavelength routed networks. It is seen that the blocking probability of traffic requests decreases as the wavelength conversion factor increases. We explode the possibility for network with different size with variation in wavelength per link. In this work the evaluation of wavelength routed op...

  5. LTE Network Radio Planning

    Directory of Open Access Journals (Sweden)

    I. R. Maravić

    2012-06-01

    Full Text Available In this paper different ways of planning the radio resources within an LTE network are analyzed. All simulations were carried out using 3GPP recommendations. Soft frequency reuse (SFR, soft fractional frequency reuse (SFFR and hard fractional frequency reuse (HFFR radio resource allocation schemes are compared to fixed frequency reuse 1 (R1 and reuse 3 (R3 radio resource allocation schemes. An optimum way of planning radio resources in a LTE network is proposed at the end of paper.

  6. A Multi-wavelength study of the M dwarf binary YY Geminorum

    CERN Document Server

    Butler, C J; Budding, E; Doyle, J G; Foing, B; Bromage, G E; Kellett, B J; Frueh, M; Huovelin, J; Brown, A; Neff, J E

    2015-01-01

    We review the results of the 1988 multi-wavelength campaign on the late-type eclipsing binary YY Geminorum. Observations include: broad-band optical and near infra-red photometry, simultaneous optical and ultraviolet (IUE) spectroscopy, X-ray (Ginga) and radio (VLA) data. From models fitted to the optical light curves, fundamental physical parameters have been determined together with evidence for transient maculations (spots) located near quadrature longitudes and intermediate latitudes. Eclipses were observed at optical, ultraviolet and radio wavelengths. Significant drops in 6cm radio emission near the phases of both primary and secondary eclipse indicate relatively compact radio emitting volumes that may lie between the binary components. IUE observations during secondary eclipse are indicative of a uniform chromosphere saturated with MgII plage-type emission and an extended volume of Ly$\\alpha$ emission. Profile fitting of high-dispersion H alpha spectra confirms the chromospheric saturation and indicate...

  7. Commercial Radio as Communication.

    Science.gov (United States)

    Rothenbuhler, Eric W.

    1996-01-01

    Compares the day-to-day work routines of commercial radio with the principles of a theoretical communication model. Illuminates peculiarities of the conduct of communication by commercial radio. Discusses the application of theoretical models to the evaluation of practicing institutions. Offers assessments of commercial radio deriving from…

  8. A graphical tool for demonstrating the techniques of radio interferometry

    International Nuclear Information System (INIS)

    We present a graphical interface designed to demonstrate the techniques of radio interferometry used by telescopes like ALMA, e-Merlin, the JVLA and SKA, in a manner accessible to the general public. Interferometry is an observational technique used by astronomers to combine the signal from a few to tens to hundreds of individual small antennas to achieve high resolution images at radio and millimetre wavelengths. This graphical interface demonstrates how the number of antenna, their position relative to one another and the rotation of the Earth allow astronomers to create highly detailed images at long wavelengths. (paper)

  9. A VLA 3.6 centimeter survey of N-type carbon stars

    Science.gov (United States)

    Luttermoser, Donald G.; Brown, Alexander

    1992-01-01

    The results are presented of a VLA-continuum survey of 7 N-type carbon stars at 3.6 cm. Evidence exists for hot plasma around such stars; the IUE satellite detected emission lines of singly ionized metals in the optically brightest carbon stars, which in solar-type stars indicate the existence of a chromosphere. In the past, these emission lines were used to constrain the lower portion of the archetypical chromospheric model of N-type carbon stars, that of TX Psc. Five of the survey stars are semiregular (1 SRa and 4 SRb) variables and two are irregular (Lb) variables. Upper limits of about 0.07 mJy are set of the SRb and Lb variables and the lone SRa (V Hya) was detected with a flux of 0.22 mJy. The upper limits for the six stars that are not detected indicate that the temperature in their winds is less than 10,000 K. Various scenarios for the emission from V Hya are proposed, and it is suggested that the radio continuum is shock-related (either due to pulsation or the suspected bipolar jet) and not due to a supposed accretion disk around an unseen companion.

  10. Aperture synthesis observations of the 21 centimeter Zeeman effect toward Orion A

    International Nuclear Information System (INIS)

    The VLA has been used to map the 21 cm Zeeman effect at 40 arcsec resolution in the absorbing H I gas in front of Orion A. Two such regions exist having typical velocities of 1 and 5 km/s; both almost certainly lie close to the H II region. Field strengths exceed 100 micro G in this H I gas. The field in the higher velocity component has been reliably detected across most of the continuum source. No field reversals exist. The distribution of line-of-sight field strengths derived for this component mimics that of tau(H I) for positions where the lines are not saturated, suggesting that the mass-to-flux ratio in this gas is approximately constant. The distribution of visual extinction across Orion A using existing radio and optical data is rederived. Maxima and minima of extinction are generally coincident with maxima and minima of magnetic field. This correspondence suggests that the observed association between field strength and tau(H I) is a real column density effect, that the effect encompasses all neutral gas in front of the source, and that the mass-to-flux ratio for this neutral gas is approximately constant. Results for Orion A lend weight to the conclusion that magnetic fields play a crucial role in the dynamics of interstellar material. 48 references

  11. Solar flares at submillimeter wavelengths

    Czech Academy of Sciences Publication Activity Database

    Krucker, S.; Gimenez de Castro, C.G.; Hudson, H. S.; Trottet, G.; Bastian, T.S.; Hales, A.S.; Kašparová, Jana; Klein, K. L.; Kretzschmar, M.; Luethi, T.; Mackinnon, A.; Pohjolainen, S.; White, S.M.

    2013-01-01

    Roč. 21, č. 1 (2013), 58/1-58/45. ISSN 0935-4956 Institutional support: RVO:67985815 Keywords : Sun * flares * radio observations Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 13.312, year: 2013

  12. An Early & Comprehensive Millimeter and Centimeter Wave and X-ray Study of Supernova 2011dh: A Non-Equipartition Blastwave Expanding into A Massive Stellar Wind

    CERN Document Server

    Horesh, Assaf; Fox, Derek B; Frail, Dale A; Carpenter, John; Kulkarni, S R; Ofek, Eran O; Gal-Yam, Avishay; Kasliwal, Mansi M; Arcavi, Iair; Quimby, Robert; Cenko, S Bradley; Nugent, Peter E; Bloom, Joshua S; Law, Nicholas M; Poznanski, Dovi; Gorbikov, Evgeny; Polishook, David; Yaron, Ofer; Ryder, Stuart; Weiler, Kurt W; Bauer, Franz; Van Dyk, Schuyler D; Immler, Stefan; Panagia, Nino; Pooley, Dave; Kassim, Namir

    2012-01-01

    Only a handful of supernovae (SNe) have been studied in multi-wavelength from radio to X-rays, starting a few days after explosion. The early detection and classification of the nearby type IIb SN2011dh/PTF11eon in M51 provides a unique opportunity to conduct such observations. We present detailed data obtained at the youngest phase ever of a core-collapse supernova (days 3 to 12 after explosion) in the radio, millimeter and X-rays; when combined with optical data, this allows us to explore the early evolution of the SN blast wave and its surroundings. Our analysis shows that the expanding supernova shockwave does not exhibit equipartition (e_e/e_B ~ 1000), and is expanding into circumstellar material that is consistent with a density profile falling like R^-2. Within modeling uncertainties we find an average velocity of the fast parts of the ejecta of 15,000 +/- 1800 km/s, contrary to previous analysis. This velocity places SN 2011dh in an intermediate blast-wave regime between the previously defined compact...

  13. VARIABLE AND TRANSIENT RADIO SOURCES IN THE FIRST SURVEY

    International Nuclear Information System (INIS)

    A comprehensive search for variable and transient radio sources has been conducted using ∼55,000 snapshot images of the Faint Images of the Radio Sky at Twenty-cm survey. We present an analysis leading to the discovery of 1627 variable and transient objects down to mJy levels over a wide range of timescales (a few minutes to years). Variations observed range from 20% to a factor of 25. Multi-wavelength matching for counterparts reveals the diverse classes of objects exhibiting variability, ranging from nearby stars and pulsars to galaxies and distant quasars. Interestingly, more than half of the objects in the sample have either no classified counterparts or no corresponding sources at any other wavelength and require multi-wavelength follow-up observations. We discuss these classes of variables and speculate on the identity of objects that lack multi-wavelength counterparts.

  14. Put a Short-Wave Radio in Your Foreign Language Classroom

    Science.gov (United States)

    Oksenholt, Svein

    1977-01-01

    Advantages of the short-wave radio as a supplement to foreign language instruction as well as practical hints on wavelength, antenna, and techniques for use are provided. Selective annotated bibliography. (STS)

  15. Ham radio for dummies

    CERN Document Server

    Silver, H Ward

    2013-01-01

    An ideal first step for learning about ham radio Beyond operating wirelessly, today's ham radio operators can transmit data and pictures; use the Internet, laser, and microwave transmitters; and travel to places high and low to make contact. This hands-on beginner guide reflects the operational and technical changes to amateur radio over the past decade and provides you with updated licensing requirements and information, changes in digital communication (such as the Internet, social media, and GPS), and how to use e-mail via radio. Addresses the critical use of ham radio for replacing downe

  16. Spectropolarimetry of Radio-Selected Broad Absorption Line Quasars

    OpenAIRE

    DiPompeo, M. A.; Brotherton, M. S.; Becker, R. H.; Tran, H. D.; Gregg, M. D.; White, R L; Laurent-Muehleisen, S. A.

    2010-01-01

    We report spectropolarimetry of 30 radio-selected broad absorption line (BAL) quasars with the Keck Observatory, 25 from the sample of Becker et al. (2000). Both high and low-ionization BAL quasars are represented, with redshifts ranging from 0.5 to 2.5. The spectropolarimetric properties of radio-selected BAL quasars are very similar to those of radio-quiet BAL quasars: a sizeable fraction (20%) show large continuum polarization (2-10%) usually rising toward short wavelengths, emission lines...

  17. Large, highly organized radio structures near the galactic centre

    Energy Technology Data Exchange (ETDEWEB)

    Yusef-Zadeh, F.; Chance, D. (Columbia Univ., New York (USA). Dept. of Astronomy); Morris, M. (California Univ., Los Angeles (USA). Dept. of Astronomy)

    1984-08-16

    A radio map of the galactic centre made at a wavelength of 20 cm with the Very Large Array telescope reveals that most of the radio emission arising within 50 pc of the galactic centre is not associated with ionizing radiation from recently formed stars. Rather, the large-scale geometry and the measured polarization of the radio emission strongly suggest that the nonthermally emitting gas is arranged along magnetic structures indicative of a substantial poloidal component to the magnetic field in the central region of the Galaxy.

  18. Large, highly organized radio structures near the galactic centre

    International Nuclear Information System (INIS)

    A radio map of the galactic centre made at a wavelength of 20 cm with the Very Large Array telescope reveals that most of the radio emission arising within 50 pc of the galactic centre is not associated with ionizing radiation from recently formed stars. Rather, the large-scale geometry and the measured polarization of the radio emission strongly suggest that the nonthermally emitting gas is arranged along magnetic structures indicative of a substantial poloidal component to the magnetic field in the central region of the Galaxy. (author)

  19. Radio Loud and Radio Quiet Quasars

    CERN Document Server

    Kellermann, K I; Kimball, A E; Perley, R A; Ivezic, Zeljko

    2016-01-01

    We discuss 6 GHz JVLA observations covering a volume-limited sample of 178 low redshift ($0.2 5 \\mathrm{~mJy~beam}^{-1}$ ($log(L) \\gtrsim 24$). The radio luminosity function of optically selected QSOs and the extended radio emission associated with RLQs are both inconsistent with simple "unified" models that invoke relativistic beaming from randomly oriented QSOs to explain the difference between RLQs and RQQs. Some intrinsic property of the AGNs or their host galaxies must also determine whether or not a QSO appears radio loud.

  20. Ground-Based Centimeter, Millimeter, and Submillimeter Observations of Comet 103P/Hartley 2

    Science.gov (United States)

    Milam, S. N.; Charnley, S. B.; Chuang, Y.-L.; Kuan, Y.-J.; Coulson, I. M.; Remijan, A. R.

    2011-01-01

    Comets provide important clues to the physical and chemical processes that occurred during the formation and early evolution of the Solar System, and could also have been important for initiating prebiotic chemistry on the early Earth [1]. Comets are comprised of molecular ices, that may be pristine interstellar remnants of Solar System formation, along with high-temperature crystalline silicate dust that is indicative of a more thermally varied history in the protosolar nebula [2]. Comparing abundances of cometary parent volatiles, and isotopic fractionation ratios, to those found in the interstellar medium, in disks around young stars, and between cometary families, is vital to understanding planetary system formation and the processing history experienced by organic matter in the so-called interstellar-comet connection [3]. We have conducted observations, at primarily millimeter and submillimeter wavelengths, where molecular emission is easily resolved, towards comets to determine important cosmogonic quantities, such as the ortl1o:pal'a ratio and isotope ratios, as well as probe the origin of cometary organics. Comets provide important clues to the processes that occurred during the formation and early evolution of the Solar System. Past observations, as well as laboratory measurements of cometary material obtained from Stardust, have shown that comets appear to contain a mixture of the products from both interstellar and nebular chemistries. A major observational challenge in cometary science is to quantify the extent to which chemical compounds can be linked to either reservoir.

  1. Radiography of Spanish Radio

    Directory of Open Access Journals (Sweden)

    Dra. Emma Rodero Antón

    2007-01-01

    Full Text Available In its eighty years of existence, radio has been always characterized to adapt to the social, cultural and technological transformations. Thus it has been until this moment. Nevertheless, some years ago, the authors and professionals of this medium have been detecting a stagnation that affects to its structure. At a time in continuous technological evolution, radio demands a deep transformation. For that reason, from the conviction of which the future radio, public and commercial, will necessarily have to renew itself, in this paper we establish ten problems and their possible solutions to the radio crisis in order to draw an x-ray of radio in Spain. Radio has future, but it is necessary to work actively by it. That the radio continues being part of sound of our life, it will depend on the work of all: companies, advertisers, professionals, students, investigators and listeners.

  2. Survey Layanan Publik Pemantauan Frekuensi Radio untuk Radio Amatir Dan Radio Antar Penduduk Indonesia

    OpenAIRE

    Azwar Aziz

    2014-01-01

    Berlatar belakang fenomena penggunaan amatir radio dan komunikasi radio antar penduduk yang berkaitan dengan faktor layanan publik dari monitor frekuensi radio, dimana peneliti memfokuskan pada permasalahan kondisi pelayanan publik yang diberikan oleh pemerintah tentang penggunaan radio non komersial yang digunakan oleh perorangan. Penelitian ini memperlihatkan penggiat amatir radio dan komunikasi radio antar penduduk bervariasi, mulai dari yang tidak mempunyai izin sampai pada yang memiliki ...

  3. Parallel Calibration for Sensor Array Radio Interferometers

    CERN Document Server

    Brossard, Martin; Pesavento, Marius; Boyer, Rémy; Larzabal, Pascal; Wijnholds, Stefan J

    2016-01-01

    In order to meet the theoretically achievable imaging performance, calibration of modern radio interferometers is a mandatory challenge, especially at low frequencies. In this perspective, we propose a novel parallel iterative multi-wavelength calibration algorithm. The proposed algorithm estimates the apparent directions of the calibration sources, the directional and undirectional complex gains of the array elements and their noise powers, with a reasonable computational complexity. Furthermore, the algorithm takes into account the specific variation of the aforementioned parameter values across wavelength. Realistic numerical simulations reveal that the proposed scheme outperforms the mono-wavelength calibration scheme and approaches the derived constrained Cram\\'er-Rao bound even with the presence of non-calibration sources at unknown directions, in a computationally efficient manner.

  4. The Contribution of Radio Selected Star Forming Galaxies to the IR Energy Density Budget

    CERN Document Server

    Seymour, N; Moss, D; McHardy, I; Zoghbi, A; Rieke, G; Page, M; Hopkins, A; Loaring, N

    2008-01-01

    We have used several different methods (radio morphology, radio spectral index, mid-IR to radio and near-IR to radio flux density ratios) to discriminate between AGN and SFGs in faint, sub-mJy radio surveys. We find that the latter two methods are the most powerful with current multi-wavelength data, but that future radio surveys with eMERLIN, LOFAR etc. (and ultimately the SKA) will greatly increase the power of the morphology and spectral index methods. As an example of the science possible we derive the IR luminosity density from the radio-selected SFGs using the radio/IR luminosity correlation. We also examine the contribution by luminosity to the total IR luminosity density and find evidence that fraction of LIRGs remains constant or decreases above z=1 while the relative fraction of ULIRGs continues to increase up to z=2.5.

  5. The PEP Survey: Infrared Properties of Radio-Selected AGN

    CERN Document Server

    Magliocchetti, M; Rosario, D; Berta, S; Floc'h, E Le; Magnelli, B; Pozzi, F; Riguccini, L; Santini, P

    2014-01-01

    By exploiting the VLA-COSMOS and the Herschel-PEP surveys, we investigate the Far Infrared (FIR) properties of radio-selected AGN. To this purpose, from VLA-COSMOS we considered the 1537, F[1.4 GHz]>0.06 mJy sources with a reliable redshift estimate, and sub-divided them into star-forming galaxies and AGN solely on the basis of their radio luminosity. The AGN sample is complete with respect to radio selection at all z<~3.5. 832 radio sources have a counterpart in the PEP catalogue. 175 are AGN. Their redshift distribution closely resembles that of the total radio-selected AGN population, and exhibits two marked peaks at z~0.9 and z~2.5. We find that the probability for a radio-selected AGN to be detected at FIR wavelengths is both a function of radio power and redshift, whereby powerful sources are more likely to be FIR emitters at earlier epochs. This is due to two distinct effects: 1) at all radio luminosities, FIR activity monotonically increases with look-back time and 2) radio activity of AGN origin i...

  6. Multifrequency Studies of Bright Radio Supernova Remnants. III. X-Ray and Radio Observations of 3C 397

    OpenAIRE

    Dyer, K. K.; Reynolds, S. P.

    1999-01-01

    Radio-bright, presumably young supernova remnants offer the opportunity of studying strong-shock physics and the nature of the interaction of ejected material with the surrounding medium. We use VLA and ROSAT images of the radio-bright supernova remnant 3C 397 (G41.1--0.3) to examine the shock structure in both thermal X-ray emission and nonthermal radio emission. The unusual rectangular morphology can be seen in VLA maps at 20 and 6 cm wavelength at a resolution of 6", and in ROSAT HRI image...

  7. Analisis Kendala Perizinan Spektrum Frekuensi Radio untuk Radio Komunitas

    OpenAIRE

    Sri Wahyuningsih

    2014-01-01

    Izin penggunaan spektrum frekuensi radio diatur dalam Undang-undang No.36 tahun 1999 tentang Telekomunikasi. Saat ini masih ditemukan Radio Komunitas yang belum memiliki Izin Stasiun Radio (ISR). Penelitian ini bertujuan untuk menemu kenali kendala-kendala yang dihadapi Radio Komunitas pada proses pengajuan Izin Stasiun Radio (ISR). Teknik pengumpulan data melalui wawancara dengan penanggungjawab Radio Komunitas dan pejabat di lingkungan Balai Monitor Frekuensi Radio (Balmon) di Jakarta, Sema...

  8. Radio Frequency Interference Mitigation in Radio Astronomy

    OpenAIRE

    Boonstra, A.J.

    2005-01-01

    The next generation of radio telescopes is expected to be one to two orders of magnitude more sensitive than the current generation. Examples of such new telescopes are the Low Frequency Array (LOFAR), currently under construction in the Netherlands, and the Square Kilometer Array (SKA), currently in a concept study phase. Another trend is that technological advances in the fields of electronics and communications systems have led to a vast increase in radio communication applications and sys...

  9. Cassini Radio and Plasma Wave Observations at Saturn

    Science.gov (United States)

    Gurnett, D. A.; Kurth, W. S.; Hospodarsky, G. B.; Persoon, A. M.; Averkamp, T. F.; Ceccni, B.; Lecacheux, A.; Zarka, P.; Canu, P.; Cornilleau-Wehrlin, N.

    2005-01-01

    Results are presented from the Cassini radio and plasma wave instrument during the approach and first few orbits around Saturn. During the approach the intensity modulation of Saturn Kilometric Radiation (SKR) showed that the radio rotation period of Saturn has increased to 10 hr 45 min plus or minus 36 sec, about 6 min longer than measured by Voyager in 1980-81. Also, many intense impulsive radio signals called Saturn Electrostatic Discharges (SEDs) were detected from saturnian lightning, starting as far as 1.08 AU from Saturn, much farther than terrestrial lightning can be detected from Earth. Some of the SED episodes have been linked to cloud systems observed in Saturn s atmosphere by the Cassini imaging system. Within the magnetosphere plasma wave emissions have been used to construct an electron density profile through the inner region of the magnetosphere. With decreasing radial distance the electron density increases gradually to a peak of about 100 per cubic centimeter near the outer edge of the A ring, and then drops precipitously to values as low as .03 per cubic centimeter over the rings. Numerous nearly monochromatic whistler-mode emissions were observed as the spacecraft passed over the rings that are believed to be produced by meteoroid impacts on the rings. Whistlermode emissions, similar to terrestrial auroral hiss were also observed over the rings, indicating that an electrodynamic interaction, similar to auroral particle acceleration, may be occurring in or near the rings. During the Titan flybys Langmuir probe and plasma wave measurements provided observations of the density and temperature in Titan's ionosphere.

  10. DMMW: A tool for multi-wavelength dark matter searches

    International Nuclear Information System (INIS)

    The level of emission expected from Dark Matter annihilation at radio frequencies, UV and at X-ray frequencies is comparable, and thus complementary, to searches in gamma rays with Fermi-LAT. However, unlike the prompt gamma-ray emission, the secondary inverse Compton, bremsstrahlung and synchrotron emission from leptons depends on the transport setup and the astrophysical properties of the object under consideration. At the same time Cosmic Ray electrons and positrons, as well as protons form a background which is subject to the same transport model uncertainties. Here we present first results from DMMW (Dark Matter Multi-Wavelength), a tool which is capable of simultaneously fitting the multi-wavelength emission spectrum of a given object for generic Dark Matter models, density distributions and Cosmic Ray transport setups. DMMW allows the user to make reliable predictions about the radio, UV, X-ray and soft gamma-ray emission associated with the relativistic electrons and positrons produced in Dark Matter annihilation, as well as the relativistic electrons, positrons and protons produced in Cosmic Ray sources and Cosmic Ray interactions with the gas. The stable charged annihilation products are propagated in the same framework as the Cosmic Rays, thus allowing the user to probe different transport setups and self-consistently constrain a possible signal from Dark Matter Annihilation from radio to soft gamma-rays.

  11. Compact Radio Sources in NGC 660

    Science.gov (United States)

    Wiercigroch, A. B.

    1995-12-01

    The nuclei of starburst galaxies are often obscured by dust and hence are probed best in non-visual wavelength regimes such as the infrared and radio. For example, radio studies of classical starburst galaxies such as NGC 253 and M82 have identified ~ 50 compact sources in each galaxy. One of the purposes of this type of observing program has been to classify the compact radio sources as H II regions or radio supernovae, and to estimate the supernova rates. If obtainable, spectral indices are used to identify the compact structures; otherwise supporting evidence or assumptions are needed. NGC 660, located at a distance of 7.5 Mpc, is a strong candidate for a search for compact radio sources. It is a relatively strong infrared emitter, has far infrared colors similar to NGC 253 and M82, and shows several peaks in published Very Large Array (VLA) maps at 6 cm and 20 cm. We therefore observed NGC 660 at 3.6 cm in the A-configuration of the VLA on 1995 July 13--14. Total integration time on-source was 4.8 hrs. The image shows a large family ( ~ 20) of compact radio structures with a flux density range of 0.1--3.4 mJy, three of which have fluxes > 2.0 mJy. The source luminosities are comparable to those of the stronger sources in M82 and NGC 253, typically a few times more powerful than Cas A. A number of the compact sources appear to lie along a ring projected against the more diffuse radio emission in the galaxy's nuclear region. The work described in this paper was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  12. Growth of centimeter-scale atomically thin MoS2 films by pulsed laser deposition

    International Nuclear Information System (INIS)

    We are reporting the growth of single layer and few-layer MoS2 films on single crystal sapphire substrates using a pulsed-laser deposition technique. A pulsed KrF excimer laser (wavelength: 248 nm; pulse width: 25 ns) was used to ablate a polycrystalline MoS2 target. The material thus ablated was deposited on a single crystal sapphire (0001) substrate kept at 700 °C in an ambient vacuum of 10−6 Torr. Detailed characterization of the films was performed using atomic force microscopy (AFM), Raman spectroscopy, UV-Vis spectroscopy, and photoluminescence (PL) measurements. The ablation of the MoS2 target by 50 laser pulses (energy density: 1.5 J/cm2) was found to result in the formation of a monolayer of MoS2 as shown by AFM results. In the Raman spectrum, A1g and E12g peaks were observed at 404.6 cm−1 and 384.5 cm−1 with a spacing of 20.1 cm−1, confirming the monolayer thickness of the film. The UV-Vis absorption spectrum exhibited two exciton absorption bands at 672 nm (1.85 eV) and 615 nm (2.02 eV), with an energy split of 0.17 eV, which is in excellent agreement with the theoretically predicted value of 0.15 eV. The monolayer MoS2 exhibited a PL peak at 1.85 eV confirming the direct nature of the band-gap. By varying the number of laser pulses, bi-layer, tri-layer, and few-layer MoS2 films were prepared. It was found that as the number of monolayers (n) in the MoS2 films increases, the spacing between the A1g and E12g Raman peaks (Δf) increases following an empirical relation, Δf=26.45−(15.42)/(1+1.44 n0.9) cm−1

  13. Growth of centimeter-scale atomically thin MoS2 films by pulsed laser deposition

    Directory of Open Access Journals (Sweden)

    Gene Siegel

    2015-05-01

    Full Text Available We are reporting the growth of single layer and few-layer MoS2 films on single crystal sapphire substrates using a pulsed-laser deposition technique. A pulsed KrF excimer laser (wavelength: 248 nm; pulse width: 25 ns was used to ablate a polycrystalline MoS2 target. The material thus ablated was deposited on a single crystal sapphire (0001 substrate kept at 700 °C in an ambient vacuum of 10−6 Torr. Detailed characterization of the films was performed using atomic force microscopy (AFM, Raman spectroscopy, UV-Vis spectroscopy, and photoluminescence (PL measurements. The ablation of the MoS2 target by 50 laser pulses (energy density: 1.5 J/cm2 was found to result in the formation of a monolayer of MoS2 as shown by AFM results. In the Raman spectrum, A1g and E12g peaks were observed at 404.6 cm−1 and 384.5 cm−1 with a spacing of 20.1 cm−1, confirming the monolayer thickness of the film. The UV-Vis absorption spectrum exhibited two exciton absorption bands at 672 nm (1.85 eV and 615 nm (2.02 eV, with an energy split of 0.17 eV, which is in excellent agreement with the theoretically predicted value of 0.15 eV. The monolayer MoS2 exhibited a PL peak at 1.85 eV confirming the direct nature of the band-gap. By varying the number of laser pulses, bi-layer, tri-layer, and few-layer MoS2 films were prepared. It was found that as the number of monolayers (n in the MoS2 films increases, the spacing between the A1g and E12g Raman peaks (Δf increases following an empirical relation, Δ f = 26 . 45 − 15 . 42 1 + 1 . 44 n 0 . 9 cm − 1 .

  14. SWOC: Spectral Wavelength Optimization Code

    Science.gov (United States)

    Ruchti, G. R.

    2016-06-01

    SWOC (Spectral Wavelength Optimization Code) determines the wavelength ranges that provide the optimal amount of information to achieve the required science goals for a spectroscopic study. It computes a figure-of-merit for different spectral configurations using a user-defined list of spectral features, and, utilizing a set of flux-calibrated spectra, determines the spectral regions showing the largest differences among the spectra.

  15. A color sensor wavelength meter

    Science.gov (United States)

    Durfee, Dallin; Jackson, Jarom; Otterstrom, Nils; Jones, Tyler; Archibald, James

    2016-05-01

    We will discuss a laser wavelength meter based on a commercial color sensor chip consisting of an array of photodiodes with different absorptive color filters. By comparing the relative amplitudes of light on the photodiodes, the wavelength of light can be determined with picometer-level precision and with picometer-scale calibration drift over a period longer than a month. This work was supported by NSF Grant Number PHY-1205736.

  16. Towards short wavelengths FELs workshop

    International Nuclear Information System (INIS)

    This workshop was caged because of the growing perception in the FEL source community that recent advances have made it possible to extend FEL operation to wavelengths about two orders of magnitude shorter than the 240 nm that has been achieved to date. In addition short wavelength FELs offer the possibilities of extremely high peak power (several gigawatts) and very short pulses (of the order of 100 fs). Several groups in the USA are developing plans for such short wavelength FEL facilities. However, reviewers of these plans have pointed out that it would be highly desirable to first carry out proof-of-principle experiments at longer wavelengths to increase confidence that the shorter wavelength devices will indeed perform as calculated. The need for such experiments has now been broadly accepted by the FEL community. Such experiments were the main focus of this workshop as described in the following objectives distributed to attendees: (1) Define measurements needed to gain confidence that short wavelength FELs will perform as calculated. (2) List possible hardware that could be used to carry out these measurements in the near term. (3) Define a prioritized FEL physics experimental program and suggested timetable. (4) Form collaborative teams to carry out this program

  17. Senior radio listeners

    DEFF Research Database (Denmark)

    Blaakilde, Anne Leonora

    Radiobroadcasting and the hardware materialization of radio have during the 20th century changed significantly, which means that senior radio listeners have travelled along with this evolution from large, impressive radio furnitures to DAB and small, wireless, mobile devices, and from grave and...... solemn radio voices to lightharted, laughing and chatting speakers. Senior radio listerners have experienced the development and refinements of technique, content and genres. It is now expected of all media users that they are capable of crossing media, combining, juggling and jumping between various...... media platforms, not the least when listening to radio. The elder generation is no exception from this. Recently, for instance, the Danish public broadcast DR has carried out an exodus of programmes targeted for the senior segment. These programmes are removed from regular FM and sent to DAB receivers...

  18. Transient Radio Neutron Stars

    OpenAIRE

    Keane, E. F.

    2010-01-01

    Here I will review the high time resolution radio sky, focusing on millisecond scales. This is primarily occupied by neutron stars, the well-known radio pulsars and the recently identified group of transient sources known as Rotating RAdio Transients (RRATs). The RRATs appear to be abundant in the Galaxy, which at first glance may be difficult to reconcile with the observed supernova rate. However, as I will discuss, it seems that the RRATs can be explained as pulsars which are either extreme...

  19. Underwater Radio Communication

    OpenAIRE

    Fjuk, Per Øyvind Eid

    2013-01-01

    In subsea applications, there is a growing demand for high-speed wireless communication links for transmitting data between different equipment. Radio communication is constrained by the high attenuation in seawater. Only a very short range is achievable, even at low frequencies. In this thesis an independent, battery-driven radio frequency transmitter is developed and tested to investigate the properties of, and prove the concept of underwater radio communication. The transmitter is made on ...

  20. Statistical comparison of the radio granulation and calcium chromospheric network

    International Nuclear Information System (INIS)

    The results of a statistical consideration of simultaneous observations of the radio granulation made with the RATAN-600 (wavelength λ=1.35 cm) and the chromospheric network (Ca II K line breifringent filter) are presented. The observations were made on July 21 and 28 and August 3, 1976, at the epoch of minimum phase of the solar cycle. Autocorrelation spectral analysis was used to find characteristics of the spatial structure. Characteristic lengths of 44 and 122 arcs (30 and 88x103 km) in the radio wavelength range and 29, 44 and 74 arcs (22, 30 and 53x103 km) in the optical region were revealed. Comparison of the two sets of data (radio and optical) was made using the cross-correlation analysis. The coherence amounts to 0.35; 0.80 and 0.75 for the spatial wavelength of 22, 30 and 53x103 km. These results confirm the earlier conclusion concerning physical relation between radio granulation and the calcium chromospheric network. However, the presence in the radio data of the period of about 120 arcs implies that both phenomena are not identical features of the solar atmosphere

  1. A Zynq-based Cluster Cognitive Radio

    OpenAIRE

    Rooks, Kurtis M.

    2014-01-01

    Traditional hardware radios provide very rigid solutions to radio problems. Intelligent software defined radios, also known as cognitive radios, provide flexibility and agility compared to hardware radio systems. Cognitive radios are well suited for radio applications in a changing radio frequency environment, such as dynamic spectrum access. In this thesis, a cognitive radio is demonstrated where the system self reconfigures to dem...

  2. Transformations of Radio Aesthetics

    Directory of Open Access Journals (Sweden)

    Grażyna Stachyra

    2015-09-01

    Full Text Available The paper presents some remarks upon the nature of contemporary radio communications in the context of the terms “aesthetics” and “aesthetisation”. The latter, denoting a process of turning aesthetic phenomena into unaesthetic ones, becomes the dominant strategy of formatted radio. The “surface aesthetisation,” which provides mainly pleasure and entertainment, transcends the simple styling of objects or environment and appears to be a more significant strand of contemporary culture. The article shows several examples of “surface” modelling of radio programming and explains their purpose in radio communication.

  3. Self-Growth of Centimeter-Scale Single Crystals by Normal Sintering Process in Modified Potassium Sodium Niobate Ceramics

    Science.gov (United States)

    Ahn, Cheol-Woo; Lee, Ho-Yong; Han, Guifang; Zhang, Shujun; Choi, Si-Young; Choi, Jong-Jin; Kim, Jong-Woo; Yoon, Woon-Ha; Choi, Joon-Hwan; Park, Dong-Soo; Hahn, Byung-Dong; Ryu, Jungho

    2015-12-01

    In this manuscript, an interesting phenomenon is reported. That is the self-growth of single crystals in Pb-free piezoelectric ceramics. These crystals are several centimeters in size. They are grown without any seed addition through a normal sintering process in modified potassium sodium niobate ceramics. It has been achieved by the composition designed to compensate the Na+ loss which occurs during the liquid phase sintering. The composition of the crystals is (K0.4925Na0.4925-xBa0.015+x/2)Nb0.995+xO3 [x is determined by the Na+ loss, due to Na2O volatilization]. These crystals have high piezoelectric voltage coefficients (g33, 131 10-3Vm/N), indicating that they are good candidates for piezoelectric sensors and energy harvesting devices. We hope that this report can offer the opportunity for many researchers to have an interest in these crystals.

  4. Centimeter-scale spatial variability in 2-methyl-4-chlorophenoxyacetic acid mineralization increases with depth in agricultural soil

    DEFF Research Database (Denmark)

    Badawi, Nora; Johnsen, Anders R.; Sørensen, Jan;

    2013-01-01

    Mineralization of organic chemicals in soil is typically studied using large homogenized samples, but little is known about the small-scale spatial distribution of mineralization potential. We studied centimeter-scale spatial distribution of 2-methyl-4-chlorophenoxyacetic acid (MCPA) mineralization...... activity at different depths (8-115 cm) in a Danish agricultural soil profi le using a 96-well microplate C-radiorespirometric method for small-volume samples. The heterotrophic microbial population and specifi c MCPA degraders decreased 10- to 100-fold from the plow layer to a depth of 115 cm. MCPA was...... mineralized in all samples in the plow layer, but only about 60% in the transition zone immediately below the plow layer showed mineralization; at greater depth even fewer samples showed mineralization. A patchy spatial distribution of mineralization activity was observed from right below the plow layer and...

  5. Investigation of the angular structure of the quasar 3C196 radio emission

    International Nuclear Information System (INIS)

    The angular dimensions and spectral characteristics are determined for the components of the preferrable brightness distribution model of the quasar 3C196 at decameter and shorter wavelengths. The physical processes are discussed that might be responsible for the extended region of radio emission that has been detected in 3C196 at decameter wavelengths

  6. Low frequency radio observations of SN 2011dh and the evolution of its post-shock plasma properties

    CERN Document Server

    Yadav, Naveen

    2016-01-01

    We present late time, low frequency observations of SN 2011dh made using the Giant Metrewave Radio Telescope (GMRT). Our observations at $325\\ \\rm MHz$, $610\\ \\rm MHz$ and $1280\\ \\rm MHz$ conducted between $93-421\\ \\rm days$ after the explosion supplement the millimeter and centimeter wave observations conducted between $4-15 \\ \\rm days$ after explosion using the Combined Array for Research in Millimeter-wave Astronomy (CARMA) and extensive radio observations ($ 1.0-36.5\\ \\rm GHz$) conducted between $16-93\\ \\rm days$ after explosion using Jansky Very Large Array (JVLA). We fit a synchrotron self absorption model (SSA) to the $610\\ \\rm MHz$ and $1280\\ \\rm MHz$ radio light curves. We use it to determine the radius ($R_{\\rm p}$) and magnetic field ($B_{\\rm p}$) at $173$ \\& $323$ days after the explosion. A comparison of the peak radio luminosity $L_{\\rm op}$, with the product of the peak frequency $\

  7. Solar observations with a low frequency radio telescope

    Science.gov (United States)

    Myserlis, I.; Seiradakis, J.; Dogramatzidis, M.

    2012-01-01

    We have set up a low frequency radio monitoring station for solar bursts at the Observatory of the Aristotle University in Thessaloniki. The station consists of a dual dipole phased array, a radio receiver and a dedicated computer with the necessary software installed. The constructed radio receiver is based on NASA's Radio Jove project. It operates continuously, since July 2010, at 20.1 MHz (close to the long-wavelength ionospheric cut-off of the radio window) with a narrow bandwidth (~5 kHz). The system is properly calibrated, so that the recorded data are expressed in antenna temperature. Despite the high interference level of an urban region like Thessaloniki (strong broadcasting shortwave radio stations, periodic experimental signals, CBs, etc), we have detected several low frequency solar radio bursts and correlated them with solar flares, X-ray events and other low frequency solar observations. The received signal is monitored in ordinary ASCII format and as audio signal, in order to investigate and exclude man-made radio interference. In order to exclude narrow band interference and calculate the spectral indices of the observed events, a second monitoring station, working at 36 MHz, is under construction at the village of Nikiforos near the town of Drama, about 130 km away of Thessaloniki. Finally, we plan to construct a third monitoring station at 58 MHz, in Thessaloniki. This frequency was revealed to be relatively free of interference, after a thorough investigation of the region.

  8. Accurate Weather Forecasting for Radio Astronomy

    Science.gov (United States)

    Maddalena, Ronald J.

    2010-01-01

    The NRAO Green Bank Telescope routinely observes at wavelengths from 3 mm to 1 m. As with all mm-wave telescopes, observing conditions depend upon the variable atmospheric water content. The site provides over 100 days/yr when opacities are low enough for good observing at 3 mm, but winds on the open-air structure reduce the time suitable for 3-mm observing where pointing is critical. Thus, to maximum productivity the observing wavelength needs to match weather conditions. For 6 years the telescope has used a dynamic scheduling system (recently upgraded; www.gb.nrao.edu/DSS) that requires accurate multi-day forecasts for winds and opacities. Since opacity forecasts are not provided by the National Weather Services (NWS), I have developed an automated system that takes available forecasts, derives forecasted opacities, and deploys the results on the web in user-friendly graphical overviews (www.gb.nrao.edu/ rmaddale/Weather). The system relies on the "North American Mesoscale" models, which are updated by the NWS every 6 hrs, have a 12 km horizontal resolution, 1 hr temporal resolution, run to 84 hrs, and have 60 vertical layers that extend to 20 km. Each forecast consists of a time series of ground conditions, cloud coverage, etc, and, most importantly, temperature, pressure, humidity as a function of height. I use the Liebe's MWP model (Radio Science, 20, 1069, 1985) to determine the absorption in each layer for each hour for 30 observing wavelengths. Radiative transfer provides, for each hour and wavelength, the total opacity and the radio brightness of the atmosphere, which contributes substantially at some wavelengths to Tsys and the observational noise. Comparisons of measured and forecasted Tsys at 22.2 and 44 GHz imply that the forecasted opacities are good to about 0.01 Nepers, which is sufficient for forecasting and accurate calibration. Reliability is high out to 2 days and degrades slowly for longer-range forecasts.

  9. Patrolling the Sky at Long Wavelengths

    Science.gov (United States)

    Taylor, Gregory B.; Obenberger, K.; Hartman, J.; LWA Collaboration

    2013-01-01

    The first station of the Long Wavelength Array, “LWA1”, is located near the center of the Very Large Array in central New Mexico and has recently begun scientific operations as a stand-alone instrument with collecting area roughly equivalent to a 100m dish. The LWA1 images the sky in near-real-time using the “transient buffer - narrowband” (TBN) system which is operational with 258 dipoles, and a bandwidth of 70 kHz. This bandwidth can be placed at any frequency between 5 and 88 MHz. Near-real-time reduction of the data is accomplished by a dedicated cluster in the electronics shelter of the array. The LWA1 can also form up to 4 beams on the sky simultaneously with 16 MHz bandwidth in each of two tunings and full polarization which can provide higher senstivity for follow-up observations. Here we report on detection limits for prompt emission from approximately 30 Gamma-Ray Bursts at frequencies between 30 and 80 MHz. We also report on a number of bright transients of short duration that were detected in the course of searching the error-boxes of GRBs. Support for operations and continuing development of the LWA1 is provided by the National Science Foundation under grant AST-1139974 of the University Radio Observatory program.

  10. Wavelength scale imaging of trapped ions for quantum networking

    Science.gov (United States)

    Streed, Erik; Norton, Benjamin; Jechow, Andreas; Petrasiunas, Matt; Kielpinski, David

    2011-05-01

    We have demonstrated wavelength scale imaging of Ytterbium ions with a microfabricated phase Fresnel lens. Near diffraction limited ion spot sizes of 440 nm (FWHM) were observed by fluorescence imaging on the 369.5 nm transition. The phase Fresnel lens was integrated in-vacuum with a needle style radio frequency Paul trap. To reduce the ion motion below the imaging resolution the ions were laser cooled close to the Doppler limit on the 369.5 nm transition This is the first demonstration of imaging trapped ions with a resolution on the order of the transition wavelength, an important step towards obtaining high efficiency mode-matching of the ion fluorescence emission to a single optical mode. Funded by the Australian Research Council and the US Air Force Office of Scientific Research.

  11. Wavelength Filters in Fibre Optics

    CERN Document Server

    Venghaus, Herbert

    2006-01-01

    Wavelength filters constitute an essential element of fibre-optic networks. This book gives a comprehensive account of the principles and applications of such filters, including their technological realisation. After an introductory chapter on wavelength division multiplexing in current and future fibre optic networks follows a detailed treatment of the phase characteristics of wavelength filters, a factor frequently neglected but of significant importance at high bit rates. Subsequent chapters cover three-dimensional reflection of gratings, arrayed waveguide gratings, fibre Bragg gratings, Fabry-Perot filters, dielectric multilayer filters, ring filters, and interleavers. The book explains the relevant performance parameters, the particular advantages and shortcomings of the various concepts and components, and the preferred applications. It also includes in-depth information on the characteristics of both commercially available devices and those still at the R&D stage. All chapters are authored by inter...

  12. Planar Lenses at Visible Wavelengths

    CERN Document Server

    Khorasaninejad, Mohammadreza; Devlin, Robert C; Oh, Jaewon; Zhu, Alexander Y; Capasso, Federico

    2016-01-01

    Sub-wavelength resolution imaging requires high numerical aperture (NA) lenses, which are bulky and expensive. Metasurfaces allow the miniaturization of conventional refractive optics into planar structures. We show that high-aspect-ratio titanium dioxide metasurfaces can be fabricated and designed as meta-lenses with NA = 0.8. Diffraction-limited focusing is demonstrated at wavelengths of 405 nm, 532 nm, and 660 nm with corresponding efficiencies of 86%, 73%, and 66%. The meta-lenses can resolve nanoscale features separated by sub-wavelength distances and provide magnification as high as 170x with image qualities comparable to a state-of-the-art commercial objective. Our results firmly establish that meta-lenses can have widespread applications in laser-based microscopy, imaging, and spectroscopy.

  13. CCIR and radio astronomy

    International Nuclear Information System (INIS)

    The role of the CCIR with regard to the implementation of the radio spectrum for astronomy is discussed. Attention is given to the weakness of signals in the radio spectrum and the avoidance of interference. Sharing of spectrum space and interference caused by transmitters operating in adjacent bands are also considered

  14. Broadcast Management: Radio; Television.

    Science.gov (United States)

    Quaal, Ward L.; Martin, Leo A.

    After outlining the qualities necessary in a good radio or television manager, the book describes his duties which fall in three major areas: programming, engineering, and sales. It discusses the relationship between the station and its audience in detail. Sections on radio and television programming describe the way most stations operate and…

  15. The Radio Jove Project

    Science.gov (United States)

    Thieman, J. R.

    2010-01-01

    The Radio love Project is a hands-on education and outreach project in which students, or any other interested individuals or groups build a radio telescope from a kit, operate the radio telescope, transmit the resulting signals through the internet if desired, analyze the results, and share the results with others through archives or general discussions among the observers. Radio love is intended to provide an introduction to radio astronomy for the observer. The equipment allows the user to observe radio signals from Jupiter, the Sun, the galaxy, and Earth-based radiation both natural and man-made. The project was started through a NASA Director's Discretionary Fund grant more than ten years ago. it has continued to be carried out through the dedicated efforts of a group of mainly volunteers. Dearly 1500 kits have been distributed throughout the world. Participation can also be done without building a kit. Pre-built kits are available. Users can also monitor remote radio telescopes through the internet using free downloadable software available through the radiosky.com website. There have been many stories of prize-winning projects, inspirational results, collaborative efforts, etc. We continue to build the community of observers and are always open to new thoughts about how to inspire the observers to still greater involvement in the science and technology associated with Radio Jove.

  16. Radio efficiency of pulsars

    CERN Document Server

    Szary, Andrzej; Melikidze, George; Gil, Janusz; Xu, Ren-Xin

    2014-01-01

    We investigate radio emission efficiency $\\xi$ of pulsars and report a near linear inverse correlation between $\\xi$ and the spindown power $\\dot E$, as well as a near linear correlation between $\\xi$ and pulsar age $\\tau$. This is a consequence of very weak, if any, dependences of radio luminosity $L$ on pulsar period $P$ and period derivative $\\dot{P}$, in contrast to X-ray or $\\gamma$-ray emission luminosities. The analysis of radio fluxes suggests that these correlations are not due to a selection effect, but are intrinsic to the pulsar radio emission physics. We have found that, although with a large variance, the radio luminosity of pulsars is $\\left\\approx 10^{29} \\,{\\rm erg/s}$, regardless of the position in the $P-\\dot P$ diagram. Within such a picture, a model-independent statement can be made that the death line of radio pulsars corresponds to an upper limit in the efficiency of radio emission. If we introduce the maximum value for a radio efficiency into Monte Carlo-based population syntheses we c...

  17. Radio Counterparts of Compact Binary Mergers detectable in Gravitational Waves: A Simulation for an Optimized Survey

    CERN Document Server

    Hotokezaka, Kenta; Hallinan, Gregg; Lazio, T Joseph W; Nakar, Ehud; Piran, Tsvi

    2016-01-01

    Mergers of binary neutron stars and black hole-neutron star binaries produce gravitational-wave (GW) emission and outflows with significant kinetic energies. These outflows result in radio emissions through synchrotron radiation of accelerated electrons in shocks formed with the circum-merger medium. We explore the detectability of these synchrotron generated radio signals by follow-up observations of GW merger events lacking a detection of electromagnetic counterparts in other wavelengths. We model radio light curves arising from (i) sub-relativistic merger ejecta and (ii) ultra-relativistic jets. The former produces radio remnants on timescales of a few years and the latter produces $\\gamma$-ray bursts in the direction of the jet and orphan radio afterglows extending over wider angles on timescales of a week to a month. The intensity and duration of these radio counterparts depend on the kinetic energies of the outflows and on circum-merger densities. We estimate the detectability of the radio counterparts ...

  18. Shocked by the Very Bright Radio Flare and Afterglow of GRB 130427A

    Science.gov (United States)

    van der Horst, Alexander J.

    2014-01-01

    Gamma-ray burst (GRB) 130427A was extremely bright across the electromagnetic spectrum, with emission spanning 16 orders of magnitude in observing frequency, from almost 100 GeV gamma-rays down to the GHz radio regime. While the intrinsic luminosity of this GRB was not extreme compared to other GRBs, it displayed the largest measured fluence of the last three decades due to its proximity with a redshift of 0.34. One of the most notable characteristics of this GRB was its bright radio emission, in particular the radio flare which has been observed only a few times in other GRBs and is usually attributed to the reverse shock moving back into the GRB jet. Here we present radio observations with unprecedented temporal coverage at three observing frequencies obtained with the Westerbork Synthesis Radio Telescope (WSRT) and the Arcminute Microkelvin Imager (AMI). AMI had the earliest radio detection at 8 hours after the initial flash of gamma-rays, catching the radio flare on the rise. The 12-hour WSRT observations in the first few days enabled a detailed study of the short time-scale behavior at radio wavelengths. Besides our observations of the radio flare and afterglow up to three months after the gamma-ray trigger, we present our results for modeling the radio light curves together with the broadband data set in various other wavelength regimes, enabling us to determine physical parameters of both the reverse and forward shock of this enigmatic GRB.

  19. Sub-wavelength plasmon laser

    Energy Technology Data Exchange (ETDEWEB)

    Bora, Mihail; Bond, Tiziana C.

    2016-04-19

    A plasmonic laser device has resonant nanocavities filled with a gain medium containing an organic dye. The resonant plasmon frequencies of the nanocavities are tuned to align with both the absorption and emission spectra of the dye. Variables in the system include the nature of the dye and the wavelength of its absorption and emission, the wavelength of the pumping radiation, and the resonance frequencies of the nanocavities. In addition the pumping frequency of the dye is selected to be close to the absorption maximum.

  20. Optical and radio variability in blazars

    Science.gov (United States)

    Hufnagel, Beth R.; Bregman, Joel N.

    1992-01-01

    An analysis is presented of the optical (0.44 micron) and radio flux density variations (4.8, 8.0, and 14.5 GHz) of the five best observed variable AGN, of which three are BL Lac objects and two are optically violent variable (OVV) quasars. For each object the nature of the variability at individual wavelengths is determined by using a structure function analysis and the autocorrelation function as calculated from the discrete correlation technique. Both techniques yield similar results, showing that the optical variations are similar for all objects and are a combination of flicker and shot noise. The radio variability is distinct, being described by shot noise (less variation at short times), with the two OVVs exhibiting the most extreme behavior. The time lag between the variations at the three radio frequencies and the optical flux is studied with the discrete cross-correlation function and the mean variance methods. It is concluded that the optical and radio emitting regions are physically related, exist on distinct time scales, and excite their synchrotron emitting plasmas differently.

  1. FIR galaxies with compact radio cores

    Science.gov (United States)

    Chini, R.; Biermann, P. L.; Kreysa, E.; Kuhr, H.; Mezger, P. G.; Schmidt, J.; Witzel, A.; Zensus, J. A.

    1987-07-01

    Comparing the IRAS point-source catalog (1985) with sources detected in a VLBI extragalactic radio source survey (Zensus et al., 1984), five FIR sources are found which all show compact radio cores. These objects have been observed with the 30-m MRT at Pico Veleta (Spain) at 1.2-mm wavelength to provide spectral coverage between IRAS and radio bands. The two galaxies among the five sources have luminosities of order 10 to the 12th solar luminosities in the FIR and thus may be super star bursters similar to Arp 220. On the other hand, all five objects have active galactic nuclei, and so the FIR luminosities may be powered by the nuclear activity. Since flat-spectrum radio sources have compact nuclear components, the 1-Jy catalog and its extension to lower flux densities (Kuehr et al., 1979 and 1981) are compared with the IRAS catalog, and a small number of additional active nuclei with strong emission in the FIR are identified. These objects can serve to study the competition between starbursts and nuclear activity to explain high FIR luminosities.

  2. Continued Radio Monitoring of the Gamma Ray Burst 991208

    CERN Document Server

    Galama, T J; Sari, R; Berger, E; Taylor, G B; Kulkarni, S R

    2003-01-01

    We present radio observations of the afterglow of the bright gamma-ray burst GRB 991208 at frequencies of 1.4, 4.9 and 8.5 GHz, taken between two weeks and 300 days after the burst. The well-sampled radio light curve at 8.5 GHz shows that the peak flux density peaked about 10 days after the burst and decayed thereafter as a power-law t^-1.07. This decay rate is more shallow than the optical afterglow with t^-2.2, which was measured during the first week. These late-time data are combined with extensive optical, millimeter and centimeter measurements and fitted to the standard relativistic blast wave model. In agreement with previous findings, we find that an isotropic explosion in a constant density or wind-blown medium cannot explain these broadband data without modifying the assumption of a single power-law slope for the electron energy distribution. A jet-like expansion provides a reasonable fit to the data. In this case, the flatter radio light curve compared to the optical may be due to emission from an ...

  3. A statistical study of SDSS radio-emitters

    CERN Document Server

    Vitale, Mariangela; García-Marín, Macarena; Eckart, Andreas; Bremer, Marcus; Valencia-S, Mónica; Zensus, Anton

    2013-01-01

    The cross-correlation of the Sloan Digital Sky Survey Data Release 7 with the Faint Images of the Radio Sky at Twenty-Centimeters survey allows for a multiwavelength statistical study of radio-optical galaxy properties on a very large number of sources. The correlation we find between $L_{[20 cm]}/L_{[H\\alpha]}$ and optical emission line ratios suggests that the origin of the emission in powerful radio-galaxies is of nuclear rather than of stellar origin. In particular, the spectroscopic classification in Seyferts, Low Ionization Narrow Emission Regions (LINERs) and star-forming galaxies provided by emission-line diagnostic diagrams peaks on the AGN region for higher $L_{[20 cm]}/L_{[H\\alpha]}$ values. The trend differs from Seyferts to LINERs. The [NII]/H$\\alpha$ vs. equivalent width of the H$\\alpha$ line diagram confirms the LINER classification for most of those that have been identified with the traditional diagnostic diagrams. A small fraction of sources seem to be powered by post-AGB stars instead.

  4. DETECTION OF RADIO EMISSION FROM FIREBALLS

    Energy Technology Data Exchange (ETDEWEB)

    Obenberger, K. S.; Taylor, G. B.; Dowell, J.; Henning, P. A.; Schinzel, F. K.; Stovall, K. [Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM 87131 (United States); Hartman, J. M. [NASA Jet Propulsion Laboratory, Pasadena, CA 91109 (United States); Ellingson, S. W. [Bradley Department of Electrical Engineering, Virginia Tech, Blacksburg, VA 24061 (United States); Helmboldt, J. F.; Wilson, T. L. [US Naval Research Laboratory, Code 7213, Washington, DC 20375 (United States); Kavic, M. [Department of Physics, Long Island University, Brooklyn, NY 11201 (United States); Simonetti, J. H. [Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States)

    2014-06-20

    We present the findings from the Prototype All-Sky Imager, a back end correlator of the first station of the Long Wavelength Array, which has recorded over 11,000 hr of all-sky images at frequencies between 25 and 75 MHz. In a search of this data for radio transients, we have found 49 long-duration (10 s of seconds) transients. Ten of these transients correlate both spatially and temporally with large meteors (fireballs), and their signatures suggest that fireballs emit a previously undiscovered low frequency, non-thermal pulse. This emission provides a new probe into the physics of meteors and identifies a new form of naturally occurring radio transient foreground.

  5. Eco-Radio Intelligente / Cognitive Green radio

    OpenAIRE

    Moy, Christophe; Palicot, Jacques

    2015-01-01

    Présentation National audience La présentation introduit les concepts de l'éco-radio intelligente et donne quelques exemples parmi ceux effectués par l'équipe SCEE de CentraleSupélec et de l'IETR à Rennes.

  6. A Bursting Radio Transient in the Direction of the Galactic Center

    CERN Document Server

    Ray, Paul S; Lazio, T Joseph; Kassim, Namir E; Roy, Subhashis; Kaplan, David L; Chakrabarty, Deepto

    2008-01-01

    The radio sky is poorly sampled for rapidly varying transients because of the narrow field-of-view of most imaging radio telescopes at cm and shorter wavelengths. The emergence of sensitive long wavelength observations with intrinsically larger fields-of-view are changing this situation, as partly illustrated by our ongoing meter-wavelength monitoring observations and archival studies of the Galactic Center. In this search, we discovered a transient, bursting, radio source in the direction of the Galactic Center, GCRT J1745-3009, with extremely unusual properties. Its flux and rapid variability imply a brightness temperature >10^12 K if it is at a distance >70 pc, implying that it is a coherent emitter. I will discuss the discovery of the source and the subsequent re-detections, as well as searches for counterparts at other wavelengths, and several proposed models.

  7. Unveiling the origin of the radio emission in radio-quiet quasars

    CERN Document Server

    Ruiz, Noelia Herrera; Norris, Ray P; Maini, Alessandro

    2016-01-01

    The origin of the radio emission in radio-quiet quasars (RQQs) has been a matter of debate for a long time. It is not well understood whether the emission is caused by star formation in the host galaxy or by black hole activity of the active galactic nuclei (AGN). We shed some light on these questions using the Very Long Baseline Interferometry (VLBI) technique to search for RQQs in the field of the Cosmological Evolution Survey (COSMOS). The extensive multi-wavelength coverage of the field (from radio to X-rays) was used to classify RQQs, and the milli-arcsecond resolution of VLBI provides a direct way to identify AGNs. In a sample of 18 RQQs we detected 3 using the Very Long Baseline Array (VLBA) at 1.4 GHz. In this letter we report for the first time on a sample of RQQs with a measured lower limit on the fraction of radio emission coming from the AGN, thus demonstrating that the radio emission of at least some RQQs is dominated by an AGN.

  8. Embracing the Wave: Using the Very Small Radio Telescope to Teach Students about Radio Astronomy

    Science.gov (United States)

    Fish, Vincent L.; Needles, M. M.; Rogers, A. E. E.; Doherty, M.; Minnigh, S.; Arndt, M. B.; Pratap, P.

    2010-01-01

    The Very Small Radio Telescope (VSRT) is a low-cost educational tool appropriate for laboratory demonstrations of the nature of radio waves and the principles of interferometry for use in both high school and undergraduate physics/astronomy classes. The system consists of small direct broadcast antenna dishes and other commercially available parts and can be assembled for under $500. Complete teaching units have been developed and tested by high school physics teachers to demonstrate radio wave transmission and exponential absorption though materials (Beer's law), the polarization of electromagnetic waves (Malus' law), the inverse square law, and interferometry. These units can be used to explore the properties of electromagnetic waves, including similarities and differences between radio and visible light, while challenging students' misconceptions about a wavelength regime that is important to both astronomy and everyday life. In addition, the VSRT can be used as a radio astronomical interferometer to measure the diameter of the Sun at 12 GHz. Full details, including a parts list, comprehensive assembly instructions, informational memos, teaching units, software, and conformance to national and Massachusetts educational standards, are available on the web at http://www.haystack.mit.edu/edu/undergrad/VSRT/index.html . Development of the VSRT at MIT Haystack Observatory is made possible through funding provided by the National Science Foundation.

  9. Large-scale radio structure of R Aquarii

    International Nuclear Information System (INIS)

    Radio continuum observations of the R Aqr symbiotic star system, using the compact D configuration of the VLA at 6-cm wavelength, reveal a large-scale about 2-arcmin structure engulfing the binary, which has long been known to have a similar optical nebula. This optical/radio nebula possesses about 4 x 10 to the 42nd ergs of kinetic energy which is typical of a recurrent nova outburst. Moreover, a cluster of a dozen additional 6-cm radio sources were observed in proximity to R Aqr, most of these discrete sources lie about 3 arcmin south and/or west of R Aqr and, coupled with previous 20-cm data, spectral indices limits suggest a thermal nature for some of these sources. If the thermal members of the cluster are associated with R Aqr, it may indicate a prehistoric eruption of the system's suspected recurrent nova. The nonthermal cluster members may be extragalactic background radio sources. 15 references

  10. The large-scale radio structure of R Aquarii

    Science.gov (United States)

    Hollis, J. M.; Michalitsianos, A. G.; Oliversen, R. J.; Yusef-Zadeh, F.; Kafatos, M.

    1987-01-01

    Radio continuum observations of the R Aqr symbiotic star system, using the compact D configuration of the VLA at 6-cm wavelength, reveal a large-scale about 2-arcmin structure engulfing the binary, which has long been known to have a similar optical nebula. This optical/radio nebula possesses about 4 x 10 to the 42nd ergs of kinetic energy which is typical of a recurrent nova outburst. Moreover, a cluster of a dozen additional 6-cm radio sources were observed in proximity to R Aqr, most of these discrete sources lie about 3 arcmin south and/or west of R Aqr and, coupled with previous 20-cm data, spectral indices limits suggest a thermal nature for some of these sources. If the thermal members of the cluster are associated with R Aqr, it may indicate a prehistoric eruption of the system's suspected recurrent nova. The nonthermal cluster members may be extragalactic background radio sources.

  11. Wavelength conversion based spectral imaging

    DEFF Research Database (Denmark)

    Dam, Jeppe Seidelin

    resolution for this spectral region. Today, an increasing number of applications exists outside the spectral region covered by Si-based devices, e.g. within cleantech, medical or food imaging. We present a technology based on wavelength conversion which will extend the spectral coverage of state of the art...

  12. Radio source evolution

    CERN Document Server

    Perucho, Manel

    2015-01-01

    Baldwin (1982) wrote that "the distribution of sources in the radio luminosity, P, overall physical size, D, diagram" could be considered as "the radio astronomer's H-R diagram". However, unlike the case of stars, not only the intrinsic properties of the jets, but also those of the host galaxy and the intergalactic medium are relevant to explain the evolutionary tracks of radio radio sources. In this contribution I review the current status of our understanding of the evolution of radio sources from a theoretical and numerical perspective, using the P-D diagram as a framework. An excess of compact (linear size < 10 kpc) sources could be explained by low-power jets being decelerated within the host galaxy, as shown by recent numerical simulations. These decelerated jets could also explain the population of the radio sources that have been recently classified as FR0. I will discuss the possible tracks that radio sources may follow within this diagram, and some of the physical processes that can explain the d...

  13. Planck on Radio Sources: Data and Findings

    Science.gov (United States)

    Partridge, Robert Bruce

    2015-08-01

    Planck scanned the entire sky every six months at nine frequency bands from 28 to 857 GHz with enough sensitivity to detect over a thousand extragalactic radio sources. It thus provides measurements of the mm and sub-mm spectra of these sources in a regular cadence, even at wavelengths hard to observe from the ground. Polarization measurements (or upper limits) are provided for brighter sources at 28-353 GHz. Finally, Planck is calibrated to Planck provides on extragalactic sources, in particular the Second Planck Catalogue of Compact Sources (PCCS2), then more briefly describe some of the scientific conclusions drawn from the Planck measurments.

  14. Quantification of centimeter-scale spatial variation in PAH, glucose and benzoic acid mineralization and soil organic matter in road-side soil

    International Nuclear Information System (INIS)

    The aim of the study was to determine centimeter-scale spatial variation in mineralization potential in diffusely polluted soil. To this end we employed a 96-well microplate method to measure the mineralization of 14C-labeled organic compounds in deep-well microplates and thereby compile mineralization curves for 348 soil samples of 0.2-cm3. Centimeter-scale spatial variation in organic matter and the mineralization of glucose, benzoic acid, and PAHs (phenanthrene and pyrene) was determined for urban road-side soil sampled as arrays (7 x 11 cm) of 96 subsamples. The spatial variation in mineralization was visualized by means of 2-D contour maps and quantified by means of semivariograms. The geostatistical analysis showed that the easily degradable compounds (glucose and benzoic acid) exhibited little spatial variation in mineralization potential, whereas the mineralization was highly heterogeneous for the PAH compounds that require specialized degraders. The spatial heterogeneity should be taken into account when estimating natural attenuation rates. - Highlights: → Geostatistics were applied at the centimeter scale. → Glucose and benzoic acid mineralization showed little spatial variation. → PAH mineralization was highly variable at the sub-centimeter scale. → High spatial heterogeneity may be caused by low functional redundancy. - This study supports the hypothesis that specialized xenobiotic degraders may show high spatial heterogeneity in soil due to low functional redundancy.

  15. Modeling of radio meteors

    Energy Technology Data Exchange (ETDEWEB)

    Karpov, A.V.; Sidorov, V.V.; Tereshin, S.N. [Kazan State Univ., Tatarstan (Russian Federation)

    1995-11-01

    A modified version of a computer model of radio meteors, based on empirical data for the arrival of meteoric material in circumterrestrial space, is presented. Good agreement with the experimental data for the Moscow-Kazan radio link is obtained. Results of calculations of the angular sizes of the reflection area for the St. Petersburg-Kazan radio link are presented. The reflection area is shown to be a sufficiently compact object with angular sizes 34.6{degrees}{+-}2.1{degrees} in the azimuthal plane and 12.7{degrees}{+-}1.2{degrees} in the vertical plane.

  16. Boom Booom Net Radio

    DEFF Research Database (Denmark)

    Grimshaw, Mark Nicholas; Yong, Louisa; Dobie, Ian

    1999-01-01

    Internet radio is one of the growth areas of the Internet but, as this article will show, is fraught with difficulties and frustration for both the modestly-funded broadcaster (bitcaster) and the listener. The article will illustrate some of these problems by means of a short case study...... of an existing Internet radio station; Boom Booom Net Radio. Whilst necessity dictates some use of technology-related terminology, wherever possible we have endeavoured to keep such jargon to a minimum and to either explain it in the text or to provide further explanation in the appended glossary....

  17. Radio Kotvanen paikallisradioksi

    OpenAIRE

    Lamminen, Anssi

    2008-01-01

    Tämän opinnäytetyön aiheena oli selvityksen laatiminen oppilaitosympäristössä toimivalle radiolle paikallisradioksi saattamiseen tarvittavien toimien selvittämiseksi. Radio Kotvaselle on tehty kehittämissuunnitelma opinnäytetyönä vuonna 2006, mutta nyt haluttiin selvittää sitä, miten Internetissä ja kahvila Agoralla kuuluva Radio Kotvanen voitaisiin saattaa ei-kaupalliseksi paikallisradiokanavaksi, joka lähettää ohjelmaa omalla radiotaajuudellaan ympäri vuoden. Selvitys Radio Kotvasen saattam...

  18. Unlocking radio broadcasts

    DEFF Research Database (Denmark)

    Skov, Mette; Lykke, Marianne

    2012-01-01

    This poster reports the preliminary results of a user study uncovering the information seeking behaviour of humanities scholars dedicated to radio research. The study is part of an interdisciplinary research project on radio culture and auditory resources. The purpose of the study is to inform the...... design of information architecture and interaction design of a research infrastructure that will enable future radio and audio based research. Results from a questionnaire survey on humanities scholars‟ research interest and information needs, preferred access points, and indexing levels are reported...

  19. Unlocking radio broadcasts

    DEFF Research Database (Denmark)

    Lykke, Marianne; Skov, Mette

    2012-01-01

    This poster reports the preliminary results of a user study uncovering the information seeking behaviour of humanities scholars dedicated to radio research. The study is part of an interdisciplinary research project on radio culture and auditory resources. The purpose of the study is to inform the...... design of information architecture and interaction design of a research infrastructure that will enable future radio and audio based research. Results from a questionnaire survey on humanities scholars’ research interest and information needs, preferred access points, and indexing levels are reported...

  20. Imprints of Molecular Clouds in Radio Continuum Images

    CERN Document Server

    Yusef-Zadeh, F

    2012-01-01

    We show radio continuum images of several molecular complexes in the inner Galaxy and report the presence of dark features that coincide with dense molecular clouds. Unlike infrared dark clouds, these features which we call "radio dark clouds" are produced by a deficiency in radio continuum emission from molecular clouds that are embedded in a bath of UV radiation field or synchrotron emitting cosmic ray particles. The contribution of the continuum emission along different pathlengths results in dark features that trace embedded molecular clouds. The new technique of identifying cold clouds can place constraints on the depth and the magnetic field of molecular clouds when compared to those of the surrounding hot plasma radiating at radio wavelengths. The study of five molecular complexes in the inner Galaxy, Sgr A, Sgr B2, radio Arc, the snake filament and G359.75-0.13 demonstrate an anti--correlation between the distributions of radio continuum and molecular line and dust emission. Radio dark clouds are iden...

  1. Does microbial centimeter-scale heterogeneity impact MCPA degradation in and leaching from a loamy agricultural soil?

    Science.gov (United States)

    Rosenbom, Annette E; Binning, Philip J; Aamand, Jens; Dechesne, Arnaud; Smets, Barth F; Johnsen, Anders R

    2014-02-15

    The potential for pesticide degradation varies greatly at the centimeter-scale in agricultural soil. Three dimensional numerical simulations were conducted to evaluate how such small-scale spatial heterogeneity may affect the leaching of the biodegradable pesticide 2-methyl-4-chlorophenoxyacetic acid (MCPA) in the upper meter of a variably-saturated, loamy soil profile. To incorporate realistic spatial variation in degradation potential, we used data from a site where 420 mineralization curves over 5 depths have been measured. Monod kinetics was fitted to the individual curves to derive initial degrader biomass values, which were incorporated in a reactive transport model to simulate heterogeneous biodegradation. Six scenarios were set up using COMSOL Multiphysics to evaluate the difference between models having different degrader biomass distributions (homogeneous, heterogeneous, or no biomass) and either matrix flow or preferential flow through a soil matrix with a wormhole. MCPA leached, within 250 days, below 1m only when degrader biomass was absent and preferential flow occurred. Both biodegradation in the plow layer and the microbially active lining of the wormhole contributed to reducing MCPA-leaching below 1m. The spatial distribution of initial degrader biomass within each soil matrix layer, however, had little effect on the overall MCPA-leaching. PMID:24291558

  2. A Reconfigurable Radio Architecture for Cognitive Radio in Emergency Networks

    OpenAIRE

    Zhang, Qiwei; Kokkeler, Andre B.J.; Smit, Gerard J.M.

    2006-01-01

    Cognitive Radio has been proposed as a promising technology to solve today's spectrum scarcity problem. Cognitive Radio is able to sense the spectrum to find the free spectrum, which can be optimally used by Cognitive Radio without causing interference to the licensed user. In the scope of the Adaptive Adhoc Freeband (AAF) project, an emergency network built on top of Cognitive Radio is proposed. New functional requirements and system specifications for Cognitive Radio have to be supported by...

  3. Packet Radio for Library Automation.

    Science.gov (United States)

    Brownrigg, Edwin B.; And Others

    1984-01-01

    This tutorial on packet radio (communication system using radio and digital packet-switching technology) highlights radio transmission of data, brief history, special considerations in applying packet radio to library online catalogs, technology, defining protocol at physical and network levels, security, geographic coverage, and components. (A…

  4. Social cognitive radio networks

    CERN Document Server

    Chen, Xu

    2015-01-01

    This brief presents research results on social cognitive radio networks, a transformational and innovative networking paradigm that promotes the nexus between social interactions and cognitive radio networks. Along with a review of the research literature, the text examines the key motivation and challenges of social cognitive radio network design. Three socially inspired distributed spectrum sharing mechanisms are introduced: adaptive channel recommendation mechanism, imitation-based social spectrum sharing mechanism, and evolutionarily stable spectrum access mechanism. The brief concludes with a discussion of future research directions which ascertains that exploiting social interactions for distributed spectrum sharing will advance the state-of-the-art of cognitive radio network design, spur a new line of thinking for future wireless networks, and enable novel wireless service and applications.

  5. Structure in radio galaxies

    International Nuclear Information System (INIS)

    It is shown that radio jets are a rather common phenomenon in radio galaxies. Jets can be disguised as trails in head-tail sources, bridges in double sources or simply remain undetected because of lack of resolution and sensitivity. It is natural to associate these jets with the channels which had previously been suggested to supply energy to the extended radio lobes. The observations of optical emission suggest that a continuous non-thermal spectrum extending from 109 to 1015 Hz is a common property of jets. Because significant amounts of interstellar matter are also observed in each of the galaxies surveyed it seems that models for jets which involve an interaction with this medium may be most appropriate. New information about the overall structure of extended radio sources has been obtained from the detailed multifrequency study with the WSRT. (Auth.)

  6. 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.

  7. Radio pulsar death

    CERN Document Server

    Zhang, B

    2003-01-01

    Pulsar radio emission is believed to be originated from the electron-positron pairs streaming out from the polar cap region. Pair formation, an essential condition for pulsar radio emission, is believed to be sustained in active pulsars via one photon process from either the curvature radiation (CR) or the inverse Compton scattering (ICS) seed photons, or sometimes via two photon process. In pulsars with super-critical magnetic fields, some more exotic processes, such as magnetic photon splitting and bound pair formation, will also play noticeable roles. All these effects should be synthesized to discuss radio pulsar death both in the conventional long-period regime due to the turnoff of the active gap, and in the high magnetic field regime due to the possible suppression of the free pair formation. Here I briefly review some recent progress in understanding radio pulsar death.

  8. Music, Radio, and Mediatization

    DEFF Research Database (Denmark)

    Krogh, Mads; Michelsen, Morten

    2016-01-01

    Mediatization has become a key concept for understanding the relations between media and other cultural and social fields. Contributing to the discussions related to the concept of mediatization, this article discusses how practices of radio and music(al life) influence each other. We follow Deacon......’s and Stanyer’s advice to supplement the concept of mediatization with ‘a series of additional concepts at lower levels of abstraction’ and suggest, in this respect, the notion of heterogeneous milieus of music– radio. Hereby, we turn away from the all-encompassing perspectives related to the concept of...... mediatization where media as such seem to be ascribed agency. Instead, we consider historical accounts of music–radio in order to address the complex non- linearity of concrete processes of mediatization as they take place in the multiple meetings between a decentred notion of radio and musical life....

  9. The Sardinia Radio Telescope

    Science.gov (United States)

    D'Amico, Nichi

    2011-08-01

    We present the status of the Sardinia Radio Telescope (SRT) project, a new general purpose, fully steerable 64 m diameter parabolic radio telescope under construction in Sardinia. The instrument is funded by Italian Ministry of University and Research (MIUR), by the Sardinia Regional Government (RAS), and by the Italian Space Agency (ASI), and it is charge to three research structures of the National Institute for Astrophysics (INAF): the Institute of Radio Astronomy of Bologna, the Cagliari Astronomical Observatory (in Sardinia), and the Arcetri Astrophysical Observatory in Florence. The radio telescope has a shaped Gregorian optical configuration with a 8 m diameter secondary mirror and additional Beam-Wave Guide (BWG) mirrors. One of the most challenging feature of SRT is the active surface of the primary reflector which provides good efficiency up to about 100 GHz. This paper reports on the most recent advances of the construction.

  10. Smart Radio Spectrum Management for Cognitive Radio

    Directory of Open Access Journals (Sweden)

    Partha Pratim Bhattacharya

    2011-08-01

    Full Text Available Today’s wireless networks are characterized by fixed spectrum assignment policy. The limited availablespectrum and the inefficiency in the spectrum usage necessitate a new communication paradigm toexploit the existing wireless spectrum opportunistically. Cognitive radio is a paradigm for wirelesscommunication in which either a network or a wireless node changes its transmission or receptionparameters to communicate efficiently avoiding interference with licensed or unlicensed users. It cancapture best available spectrum to meet user communication requirements (spectrum management. Inthis work, a fuzzy logic based system for spectrum management is proposed where the radio can shareunused spectrum depending on parameters like distance, signal strength, node velocity and availabilityof unused spectrum. The system is simulated and is found to give satisfactory results.

  11. Wavelength Selection in Gyrotactic Bioconvection.

    Science.gov (United States)

    Ghorai, S; Singh, R; Hill, N A

    2015-06-01

    We investigate pattern formation by swimming micro-organisms (bioconvection), when their orientation is determined by balance between gravitational and viscous torques (gyrotaxis), due to being bottom heavy. The governing equations, which consist of the Navier-Stokes equations for an incompressible fluid coupled with a micro-organism conservation equation, are solved numerically in a large cross section chamber with periodic boundary conditions in the horizontal directions. The influence of key parameters on wavelength selection in bioconvection patterns is investigated numerically. For realistic ranges of parameter values, the computed wavelengths are in good agreement with the experimental observations provided that the diffusion due to randomness in cell swimming behaviour is small, refuting a recently published claim that the mathematical model becomes inaccurate at long times. We also provide the first computational evidence of "bottom-standing" plumes in a three-dimensional simulation. PMID:25963246

  12. Short wavelength magnetic buoyancy instability

    CERN Document Server

    Mizerski, K A; Hughes, D W

    2013-01-01

    Magnetic buoyancy instability plays an important role in the evolution of astrophysical magnetic fields. Here we revisit the problem introduced by \\citet{Gilman_1970} of the short wavelength linear stability of a plane layer of compressible isothermal fluid permeated by a horizontal magnetic field of strength decreasing with height. Dissipation of momentum and magnetic field is neglected. By the use of a Rayleigh-Schr\\"odinger perturbation analysis, we explain in detail the limit in which the transverse horizontal wavenumber of the perturbation, denoted by $k$, is large (i.e.\\ short horizontal wavelength) and show that the fastest growing perturbations become localized in the vertical direction as $k$ is increased. The growth rates are determined by a function of the vertical coordinate $z$ since, in the large $k$ limit, the eigenmodes are strongly localized in the vertical direction. We consider in detail the case of two-dimensional perturbations varying in the directions perpendicular to the magnetic field,...

  13. The Dynamic Radio Sky

    OpenAIRE

    Cordes, James M.; Lazio, T. Joseph W.; McLaughlin, M. A.

    2004-01-01

    Transient radio sources are necessarily compact and usually are the locations of explosive or dynamic events, therefore offering unique opportunities for probing fundamental physics and astrophysics. In addition, short-duration transients are powerful probes of intervening media owing to dispersion, scattering and Faraday rotation that modify the signals. While radio astronomy has an impressive record obtaining high time resolution, usually it is achieved in quite narrow fields of view. Conse...

  14. Radio-learning

    OpenAIRE

    Teixeira, Marcelo Mendonça; Silva, Bento Duarte da

    2009-01-01

    The radio as a vehicle of mass communication has undergone many changes over the years through the development of informatics and cybernetics. The process of digitization suffered by conventional broadcasters and the availability of its content on the Internet, produced the latest step in the recent history of media - the Web Radio In turn, the education has been used in the new technological resources to produce educational programs multidisciplinary in several areas of knowledge and in diff...

  15. Virtual Radio Engine

    OpenAIRE

    Hossain, Riyadh

    2008-01-01

    Software Defined Radio (SDR) hardware platforms use parallel architectures. Current concepts of developing applications (such as WLAN) for these platforms are complex, because developers describe an application with hardware-specifics that are relevant to parallelism such as mapping and scheduling. To reduce this complexity, we have developed a new programming approach for SDR applications, called Virtual Radio Engine (VRE). VRE defines a language for describing applications, and a tool chain...

  16. RADIO EMISSION FROM SN 1994I IN NGC 5194 (M 51): THE BEST-STUDIED TYPE Ib/c RADIO SUPERNOVA

    International Nuclear Information System (INIS)

    We present the results of detailed monitoring of the radio emission from the Type Ic supernova SN 1994I from three days after optical discovery on 1994 March 31 until eight years later at age 2927 days on 2002 April 5. The data were mainly obtained using the Very Large Array at the five wavelengths of λλ1.3, 2.0, 3.6, 6.2, and 21 cm and from the Cambridge 5 km Ryle Telescope at λ2.0 cm. Two additional measurements were obtained at millimeter wavelengths. This data set represents the most complete, multifrequency radio observations ever obtained for a Type Ib/c supernova. The radio emission evolves regularly in both time and frequency and is well described by established supernova emission/absorption models. It is the first radio supernova with sufficient data to show that it is clearly dominated by the effects of synchrotron self-absorption at early times.

  17. Multiple wavelength observations of a solar active region

    International Nuclear Information System (INIS)

    The Solar Maximum Mission Satellite, the Sacramento Peak Vacuum Tower Telescope, the Very Large Array and the Westerbork Synthesis Radio Telescope have been used to observe active region AR 2490 on two consecutive days at soft X-ray, ultraviolet, optical and radio wavelengths (2, 6, and 20 cm), with comparable angular resolution (2'' to 15'') and field of view (4' x 4'). The radio emissions at lambda = 6 cm and 20 cm show a double structure in which one component is associated with bright Hα plage, C IV and soft X-ray emission, and the other component is associated only with sunspots. No radiation at lambda = 2 cm is detected in this latter component. Coronal temperature and emission measure derived from X-ray lines indicate that the dominant radiation mechanism of the plage-associated component is due to thermal bremsstrahlung while the gyroresonance absorption coefficient must be invoked to account for the high brightness temperature (Tsub(b) approx. equal to 2 x 106 K) observed in the sunspot associated component. The high magnetic field strength needed (600 G at a level where T approx. equal to 2 x 106 K) is explained assuming a thin transition zone, in order to reach a high electron temperature close to the sunspot, where the magnetic fields are stronger. A higher temperature gradient above sunspots is also consistent with the absence of detectable C IV emission. (orig.)

  18. How Else Can We Detect Fast Radio Bursts?

    Science.gov (United States)

    Lyutikov, Maxim; Lorimer, Duncan R.

    2016-06-01

    We discuss possible electromagnetic signals accompanying Fast Radio Bursts (FRBs) that are expected in the scenario where FRBs originate in neutron star magnetospheres. For models involving Crab-like giant pulses, no appreciable contemporaneous emission is expected at other wavelengths. However, magnetar giant flares, driven by the reconfiguration of the magnetosphere, can produce both contemporaneous bursts at other wavelengths as well as afterglow-like emission. We conclude that the best chances are: (i) prompt short GRB-like emission, (ii) a contemporaneous optical flash that can reach naked eye peak luminosity (but only for a few milliseconds), and (iii) a high-energy afterglow emission. Case (i) could be tested by coordinated radio and high-energy experiments. Case (ii) could be seen in a coordinated radio-optical surveys, e.g., by the Palomar Transient Factory in a 60 s frame as a transient object of m = 15–20 mag with an expected optical detection rate of about 0.1 hr‑1, an order of magnitude higher than in radio. Shallow, but large-area sky surveys such as ASAS-SN and EVRYSCOPE could also detect prompt optical flashes from the more powerful Lorimer-burst clones. The best constraints on the optical to radio power for this kind of emission could be provided by future observations with facilities like Large Synoptic Survey Telescope. Case (iii) might be seen in relatively rare cases that the relativistically ejected magnetic blob is moving along the line of sight.

  19. Classics in radio astronomy

    CERN Document Server

    Sullivan, Woodruff Turner

    1982-01-01

    Radio techniques were the nrst to lead astronomy away from the quiescent and limited Universe revealed by traditional observations at optical wave­ lengths. In the earliest days of radio astronomy, a handful of radio physicists and engineers made one startling discovery after another as they opened up the radio sky. With this collection of classic papers and the extensive intro­ ductory material, the reader can experience these exciting discoveries, as well as understand the developing techniques and follow the motivations which prompted the various lines of inquiry. For instance he or she will follow in detail the several attempts to detect radio waves from the sun at the turn of the century; the unravelling by Jansky of a "steady hiss type static"; the incredible story of Reber who built a 9 meter dish in his backyard in 1937 and then mapped the Milky Way; the vital discoveries by Hey and colleagues of radio bursts from the Sun and of a discrete source in the constellation of Cygnus; the development of re...

  20. Antenna Performance Analysis for Decameter Solar Radio Observations

    OpenAIRE

    Stanislavsky, Aleksander; Konovalenko, Aleksander; Abranin, Eduard; Dorovskyy, Vladimir; Mel'nik, Valentin; Kaiser, Michael; Lecacheux, Alain; Rucker, Helmut

    2011-01-01

    Decameter wavelength radio emission is finely structured in solar bursts. For their research it is very important to use a sufficient sensitivity of antenna systems. In this paper we study an influence of the radiotelescope-antenna effective area on the results of decameter solar radio observations. For this purpose we compared the solar bursts received by the array of 720 ground-based dipoles and the single dipole of the radiotelescope UTR-2. It's shown that a larger effective area of the gr...

  1. A radio pulsing white dwarf binary star

    CERN Document Server

    Marsh, T R; Hümmerich, S; Hambsch, F -J; Bernhard, K; Lloyd, C; Breedt, E; Stanway, E R; Steeghs, D T; Parsons, S G; Toloza, O; Schreiber, M R; Jonker, P G; van Roestel, J; Kupfer, T; Pala, A F; Dhillon, V S; Hardy, L K; Littlefair, S P; Aungwerojwit, A; Arjyotha, S; Koester, D; Bochinski, J J; Haswell, C A; Frank, P; Wheatley, P J

    2016-01-01

    White dwarfs are compact stars, similar in size to Earth but ~200,000 times more massive. Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, but when in close orbits with less dense stars, white dwarfs can strip material from their companions, and the resulting mass transfer can generate atomic line and X-ray emission, as well as near- and mid-infrared radiation if the white dwarf is magnetic. However, even in binaries, white dwarfs are rarely detected at far-infrared or radio frequencies. Here we report the discovery of a white dwarf / cool star binary that emits from X-ray to radio wavelengths. The star, AR Scorpii (henceforth AR Sco), was classified in the early 1970s as a delta-Scuti star, a common variety of periodic variable star. Our observations reveal instead a 3.56 hr period close binary, pulsing in brightness on a period of 1.97 min. The pulses are so intense that AR Sco's optical flux can increase by a factor of four within 30 s, and they are detectable a...

  2. Radio Investigations of the Inner Heliosphere

    Science.gov (United States)

    Bougeret, J.

    2003-12-01

    We review recent observations of the thermal and non-thermal radio radiation in the inner heliosphere. The thermal radiation can yield information on both quiescent and transient structures, while non-thermal radiation traces populations of energetic electrons associated with high energy phenomena, such as beams of energetic electrons and shock waves. Results very much depend on the type of instrument which is used: spectrograph or imager, ground-based or space-borne. The frequency range of radio sources in the inner heliosphere corresponds to the metric, decametric, hectometric, and kilometric bands. Only the metric and a small part of the decametric range can be accessed from the ground. The longer wavelengths are blocked by the terrestrial ionosphere and observations from space are required. Long wavelength require extremely long baseline interferometers in order to produce images. This has never been done from space as yet. There are some techniques, however, to determine the direction of the source centroid. We will try to provide an integrated view of the different approaches, focusing on the physical nature of the phenomena which are observed. Finally we will mention future programs in this field: Stereo, FASR, LOFAR, SIRA, LWS/Sentinels among others.

  3. A Multi-Wavelength Perspective of Flares on HR 1099: Four Years of Coordinated Campaigns

    OpenAIRE

    Osten, R. A.; Brown, A; Ayres, T. R.; Drake, S. A.; Franciosini, E.; Pallavicini, R.; Tagliaferri, G.; Stewart, R. T.; Skinner, S. L.; Linsky, J. L.

    2004-01-01

    We report on four years of multiple wavelength observations of the RS CVn system V711 Tau (HR 1099) from 1993, 1994, 1996, and 1998. This combination of radio, ultraviolet, extreme ultraviolet, and X-ray observations allows us to view, in the most comprehensive manner currently possible, the coronal and upper atmospheric variability of this active binary system. We report on the changing activity state of the system as recorded in the EUV and radio across the four years of the observations, a...

  4. Short wavelength interferometer for ITER

    International Nuclear Information System (INIS)

    There is a need for a real time, reliable density measurement compatible with the restricted access and radiation environment on ITER. Due to the large plasma path length, high density and field, refraction and Faraday rotation effects makes the use of contemporary long wavelength (>50μm) interferometers impractical. In this paper we consider the design of a short wavelength vibration compensated interferometer which allows operation without a prohibitively large vibration isolated structure and permits the optics to be conveniently mounted directly in or on the tokamak. A density interferometer design for ITER incorporating a 10.6 μm CO2 interferometer with vibration compensation provided by a 3. 39 μm HeNe laser is discussed. The proposed interferometer design requires only a small intrusion into the ITER tokamak without a large support structure, refraction and Faraday rotation problems are avoided, and it provides a density resolution of at least 0.5%. Results are presented from an interferometer installed on the DIII-D tokamak incorporating essential elements of the proposed ITER design including 10.6 and 3.39 μm lasers, a retro-reflector mounted on the vacuum wall of the DIII-D tokamak and real-time density feedback control. In this paper we consider a short wavelength interferometer design that incorporates vibration compensation for use on ITER. Our primary concern is to develop a interferometer design that will produce a reliable real time density monitor. We use the ITER conceptual design activity report as the basis of the design

  5. Note: Laser wavelength precision measurement based on a laser synthetic wavelength interferometer

    Science.gov (United States)

    Yan, Liping; Chen, Benyong; Zhang, Shihua; Liu, Pengpeng; Zhang, Enzheng

    2016-08-01

    A laser wavelength precision measurement method is presented based on the laser synthetic wavelength interferometer (LSWI). According to the linear relation between the displacements of measurement and reference arms in the interferometer, the synthetic wavelength produced by an unknown wavelength and a reference wavelength can be measured by detecting the phase coincidences of two interference signals. The advantage of the method is that a larger synthetic wavelength resulting from an unknown wavelength very close to the reference wavelength can be easily determined according to the linear relation in the interferometer. Then the unknown wavelength is derived according to the one-to-one corresponding relationship between single wavelength and synthetic wavelength. Wavelengths of an external cavity diode laser and two He-Ne lasers were determined experimentally. The experimental results show that the proposed method is able to realize a relative uncertainty on the order of 10-8.

  6. Note: Laser wavelength precision measurement based on a laser synthetic wavelength interferometer.

    Science.gov (United States)

    Yan, Liping; Chen, Benyong; Zhang, Shihua; Liu, Pengpeng; Zhang, Enzheng

    2016-08-01

    A laser wavelength precision measurement method is presented based on the laser synthetic wavelength interferometer (LSWI). According to the linear relation between the displacements of measurement and reference arms in the interferometer, the synthetic wavelength produced by an unknown wavelength and a reference wavelength can be measured by detecting the phase coincidences of two interference signals. The advantage of the method is that a larger synthetic wavelength resulting from an unknown wavelength very close to the reference wavelength can be easily determined according to the linear relation in the interferometer. Then the unknown wavelength is derived according to the one-to-one corresponding relationship between single wavelength and synthetic wavelength. Wavelengths of an external cavity diode laser and two He-Ne lasers were determined experimentally. The experimental results show that the proposed method is able to realize a relative uncertainty on the order of 10(-8). PMID:27587172

  7. Planck intermediate results. XLV. Radio spectra of northern extragalactic radio sources

    CERN Document Server

    Ade, P A R; Arnaud, M; Ashdown, M; Aumont, J; Baccigalupi, C; Banday, A J; Barreiro, R B; Bartolo, N; Battaner, E; Battye, R; Benabed, K; Bendo, G J; Benoit-Lévy, A; Bernard, J -P; Bersanelli, M; Bielewicz, P; Bonaldi, A; Bonavera, L; Bond, J R; Borrill, J; Bouchet, F R; Burigana, C; Butler, R C; Calabrese, E; Cardoso, J -F; Catalano, A; Chamballu, A; Chary, R -R; Chen, X; Chiang, H C; Christensen, P R; Clements, D L; Colombo, L P L; Combet, C; Couchot, F; Coulais, A; Crill, B P; Curto, A; Cuttaia, F; Danese, L; Davies, R D; Davis, R J; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; Dickinson, C; Diego, J M; Dole, H; Donzelli, S; Doré, O; Douspis, M; Ducout, A; Dupac, X; Efstathiou, G; Elsner, F; Enßlin, T A; Eriksen, H K; Finelli, F; Forni, O; Frailis, M; Fraisse, A A; Franceschi, E; Frejsel, A; Galeotta, S; Ganga, K; Giard, M; Giraud-Héraud, Y; Gjerløw, E; González-Nuevo, J; Górski, K M; Gregorio, A; Gruppuso, A; Hansen, F K; Hanson, D; Harrison, D L; Henrot-Versillé, S; Hernández-Monteagudo, C; Herranz, D; Hildebrandt, S R; Hivon, E; Hobson, M; Holmes, W A; Hornstrup, A; Hovest, W; Huffenberger, K M; Hurier, G; Israel, F P; Jaffe, A H; Jaffe, T R; Jones, W C; Juvela, M; Keihänen, E; Keskitalo, R; Kisner, T S; Kneissl, R; Knoche, J; Kunz, M; Kurki-Suonio, H; Lagache, G; Lähteenmäki, A; Lamarre, J -M; Lasenby, A; Lattanzi, M; Lawrence, C R; Leonardi, R; Levrier, F; Liguori, M; Lilje, P B; Linden-Vørnle, M; López-Caniego, M; Lubin, P M; Macías-Pérez, J F; Madden, S; Maffei, B; Maino, D; Mandolesi, N; Maris, M; Martin, P G; Martínez-González, E; Masi, S; Matarrese, S; Mazzotta, P; Mendes, L; Mennella, A; Migliaccio, M; Miville-Deschênes, M -A; Moneti, A; Montier, L; Morgante, G; Mortlock, D; Munshi, D; Murphy, J A; Naselsky, P; Nati, F; Natoli, P; Nørgaard-Nielsen, H U; Noviello, F; Novikov, D; Novikov, I; Oxborrow, C A; Pagano, L; Pajot, F; Paladini, R; Paoletti, D; Partridge, B; Pasian, F; Pearson, T J; Peel, M; Perdereau, O; Perrotta, F; Pettorino, V; Piacentini, F; Piat, M; Pierpaoli, E; Pietrobon, D; Plaszczynski, S; Pointecouteau, E; Polenta, G; Popa, L; Pratt, G W; Prunet, S; Puget, J -L; Rachen, J P; Reinecke, M; Remazeilles, M; Renault, C; Ricciardi, S; Ristorcelli, I; Rocha, G; Rosset, C; Rossetti, M; Roudier, G; Rubiño-Martín, J A; Rusholme, B; Sandri, M; Savini, G; Scott, D; Spencer, L D; Stolyarov, V; Sudiwala, R; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Terenzi, L; Toffolatti, L; Tomasi, M; Tristram, M; Tucci, M; Umana, G; Valenziano, L; Valiviita, J; Van Tent, B; Vielva, P; Villa, F; Wade, L A; Wandelt, B D; Watson, R; Wehus, I K; Yvon, D; Zacchei, A; Zonca, A

    2016-01-01

    Continuum spectra covering centimetre to submillimetre wavelengths are presented for a northern sample of 104 extragalactic radio sources, mainly active galactic nuclei, based on four-epoch Planck data. The nine Planck frequencies, from 30 to 857 GHz, are complemented by a set of simultaneous ground-based radio observations between 1.1 and 37 GHz. The single-survey Planck data confirm that the flattest high-frequency radio spectral indices are close to zero, indicating that the original accelerated electron energy spectrum is much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The radio spectra peak at high frequencies and exhibit a variety of shapes. For a small set of low-z sources, we find a spectral upturn at high frequencies, indicating the presence of intrinsic cold dust. Variability can generally be approximated by achromatic variations, while sources with clear signatures of evolving shocks appear to be limited to the strongest outbursts.

  8. VizieR Online Data Catalog: Infrared-faint radio sources catalog (Collier+, 2014)

    Science.gov (United States)

    Collier, J. D.; Banfield, J. K.; Norris, R. P.; Schnitzeler, D. H. F. M.; Kimball, A. E.; Filipovic, M. D.; Jarrett, T. H.; Lonsdale, C. J.; Tothill, N. F. H.

    2014-11-01

    The 20cm radio data come from the Unified Radio Catalog (URC) compiled by Kimball & Ivezic (2008AJ....136..684K). This radio catalogue combines data from the National Radio Astronomy Observatory (NRAO) VLA Sky Survey (NVSS; Condon et al., 1998, Cat. VIII/65), Faint Images of the Radio Sky at Twenty Centimeters (FIRST; Becker, White & Helfand, 1995, cat. VIII/92), Green Bank 6cm survey (GB6; Gregory et al., 1996, Cat. VIII/40), the Westerbork Northern Sky Survey (WENSS; Rengelink et al. 1997; de Bruyn et al. 2000, Cat. VIII/62) and the Sloan Digital Sky Survey Data Release 6 (SDSS DR6; Adelman-McCarthy et al., 2008, Cat. II/282). We use updated NVSS and FIRST data from the URC version 2.0 (Kimball & Ivezic, in preparation), which includes a number of new sources as well as updated positions and flux densities. The IR data come from WISE (Wright et al. (WISE Team) 2009, Cat. II/311), which is an all-sky survey centred at 3.4, 4.6, 12 and 22um (referred to as bands W1, W2, W3 and W4), with respective angular resolutions of 6.1, 6.4, 6.5 and 12.0-arcsec (full width at half-maximum, FWHM), and typical 5σ sensitivity levels of 0.08, 0.11, 1 and 6mJy, with sensitivity increasing towards the ecliptic poles. (1 data file).

  9. Radio Bubbles in Clusters

    CERN Document Server

    Dunn, R J H; Taylor, G B

    2005-01-01

    We extend our earlier work on cluster cores with distinct radio bubbles, adding more active bubbles, i.e. those with Ghz radio emission, to our sample, and also investigating ``ghost bubbles,'' i.e. those without GHz radio emission. We have determined k, which is the ratio of the total particle energy to that of the electrons radiating between 10 MHz and 10 GHz. Constraints on the ages of the active bubbles confirm that the ratio of the energy factor, k, to the volume filling factor, f lies within the range 1 < k/f < 1000. In the assumption that there is pressure equilibrium between the radio-emitting plasma and the surrounding thermal X-ray gas, none of the radio lobes has equipartition between the relativistic particles and the magnetic field. A Monte-Carlo simulation of the data led to the conclusion that there are not enough bubbles present in the current sample to be able to determine the shape of the population. An analysis of the ghost bubbles in our sample showed that on the whole they have high...

  10. Tools of radio astronomy

    CERN Document Server

    Wilson, Thomas L; Hüttemeister, Susanne

    2013-01-01

    This 6th edition of “Tools of Radio Astronomy”, the most used introductory text in radio astronomy, has been revised to reflect the current state of this important branch of astronomy. This includes the use of satellites, low radio frequencies, the millimeter/sub-mm universe, the Cosmic Microwave Background and the increased importance of mm/sub-mm dust emission. Several derivations and presentations of technical aspects of radio astronomy and receivers, such as receiver noise, the Hertz dipole and  beam forming have been updated, expanded, re-worked or complemented by alternative derivations. These reflect advances in technology. The wider bandwidths of the Jansky-VLA and long wave arrays such as LOFAR and mm/sub-mm arrays such as ALMA required an expansion of the discussion of interferometers and aperture synthesis. Developments in data reduction algorithms have been included. As a result of the large amount of data collected in the past 20 years, the discussion of solar system radio astronomy, dust em...

  11. An Evolutionary Sequence of Young Radio Galaxies

    CERN Document Server

    Collier, J D; Filipović, M D; Tothill, N F H

    2015-01-01

    We have observed the faintest sample of Gigahertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) sources to date, using the Australia Telescope Compact Array. We test the hypothesis that GPS and CSS sources are the youngest radio galaxies, place them into an evolutionary sequence along with a number of other young Active Galactic Nuclei (AGN) candidates, and search for evidence of the evolving accretion mode and its relationship to star formation. GPS/CSS sources have very small radio jets that have been recently launched from the central Supermassive Black Hole and grow in linear size as they evolve, which means that the linear size of the jets is an excellent indicator of the evolutionary stage of the AGN. We use high-resolution radio observations to determine the linear size of GPS/CSS sources, resolve their jets and observe their small-scale morphologies. We combine this with other multi-wavelength age indicators, including the spectral age, colours, optical spectra and Spectral Energy Distributio...

  12. An evolutionary sequence of young radio galaxies

    Science.gov (United States)

    Collier, J. D.; Norris, R. P.; Filipović, M. D.; Tothill, N. F. H.

    2016-02-01

    We have observed the faintest sample of Gigahertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) sources to date, using the Australia Telescope Compact Array. We test the hypothesis that GPS and CSS sources are the youngest radio galaxies, place them into an evolutionary sequence along with a number of other young active galactic nuclei (AGN) candidates, and search for evidence of the evolving accretion mode and its relationship to star formation. GPS/CSS sources have very small radio jets that have been recently launched from the central supermassive black hole and grow in linear size as they evolve, which means that the linear size of the jets is an excellent indicator of the evolutionary stage of the AGN. We use high-resolution radio observations to determine the linear size of GPS/CSS sources, resolve their jets and observe their small-scale morphologies. We combine this with other multi-wavelength age indicators, including the spectral age, colours, optical spectra, and spectral energy distribution of the host galaxy, in an attempt to assemble all age indicators into a self-consistent model. We observe the most compact sources with Very Large Baseline Interferometry, which reveals their parsec-scale structures, giving us a range of source sizes and allowing us to test what fraction of GPS/CSS sources are young and evolving.

  13. Radio Frequency-Tomography of Solar Flares

    Science.gov (United States)

    Aschwanden, M. J.

    2002-05-01

    The Frequency-Agile Solar Radiotelescope (FASR) is designed to produce simultaneous images of solar phenomena at many frequencies. A data cube with a stack of multiple frequency images can be used for tomographic reconstruction of the 3D density and temperature distribution of flares, based on the free-free emission at cm and mm wavelengths. We simulate a set of multi-frequency images for the Bastille-Day flare of 2000-July-14, based on EUV observations from TRACE and soft X-ray observations from Yohkoh. The 3D model consists of some 200 postflare loops with observationally constrained densities and temperatures. The temporal evolution involves flare plasma heating, a phase of conductive cooling, followed by a phase of radiative cooling. The images simulated at different microwave frequencies reveal a sequence of optically-thick free-free emission layers, which can be "pealed off" like onion shells with increasing radio frequency. We envision a tomographic method that yields information on the density and temperature structure of flare systems and their evolution. Comparison with EUV and soft X-ray based 3D models will also allow to quantify wave scattering at radio frequencies and provide information on small-scale inhomogeneities and wave turbulence. Besides the thermal free-free emission, radio images contain also information on coherent emission processes, such as plasma emission from electron beams and loss-cone emission from gyroresonant trapped particles, conveying information on particle acceleration processes.

  14. PHYSICAL CONSTRAINTS ON FAST RADIO BURSTS

    International Nuclear Information System (INIS)

    Fast radio bursts (FRBs) are isolated, ms radio pulses with dispersion measure (DM) of order 103 pc cm–3. Galactic candidates for the DM of high latitude bursts detected at GHz frequencies are easily dismissed. DM from bursts emitted in stellar coronas are limited by free-free absorption and those from H II regions are bounded by the nondetection of associated free-free emission at radio wavelengths. Thus, if astronomical, FRBs are probably extragalactic. FRB 110220 has a scattering tail of ∼5.6 ± 0.1 ms. If the electron density fluctuations arise from a turbulent cascade, the scattering is unlikely to be due to propagation through the diffuse intergalactic plasma. A more plausible explanation is that this burst sits in the central region of its host galaxy. Pulse durations of order ms constrain the sizes of FRB sources implying high brightness temperatures that indicates coherent emission. Electric fields near FRBs at cosmological distances would be so strong that they could accelerate free electrons from rest to relativistic energies in a single wave period

  15. New SETI Sky Surveys for Radio Pulses

    CERN Document Server

    Siemion, Andrew; McMahon, Peter; Korpela, Eric; Werthimer, Dan; Anderson, David; Bower, Geoff; Cobb, Jeff; Foster, Griffin; Lebofsky, Matt; van Leeuwen, Joeri; Mallard, William; Wagner, Mark

    2008-01-01

    Berkeley conducts 7 SETI programs at IR, visible and radio wavelengths. Here we review two of the newest efforts, Astropulse and Fly's Eye. A variety of possible sources of microsecond to millisecond radio pulses have been suggested in the last several decades, among them such exotic events as evaporating primordial black holes, hyper-flares from neutron stars, emissions from cosmic strings or perhaps extraterrestrial civilizations, but to-date few searches have been conducted capable of detecting them. We are carrying out two searches in hopes of finding and characterizing these uS to mS time scale dispersed radio pulses. These two observing programs are orthogonal in search space; the Allen Telescope Array's (ATA) "Fly's Eye" experiment observes a 100 square degree field by pointing each 6m ATA antenna in a different direction; by contrast, the Astropulse sky survey at Arecibo is extremely sensitive but has 1/3,000 of the instantaneous sky coverage. Astropulse's multibeam data is transferred via the interne...

  16. Large-Aperture Wide-Bandwidth Anti-Reflection-Coated Silicon Lenses for Millimeter Wavelengths

    Science.gov (United States)

    Datta, R.; Munson, C. D.; Niemack, M. D.; McMahon, J. J.; Britton, J.; Wollack, E. J.; Beall, J.; Devlin, M. J.; Fowler, J.; Gallardo, P.; Hubmayr, J.; Irwin, K.; Newburgh, L.; Nibarger, J. P.; Page, L.; Quijada, M. A.; Schmitt, B. L.; Staggs, S. T.; Thornton, R.; Zhang, L.

    2013-01-01

    The increasing scale of cryogenic detector arrays for sub-millimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n = 3.4, low loss, and relatively high thermal conductivity is a nearly optimal material for these purposes, but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coffecient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating. We have fabricated and coated silicon lenses as large as 33.4 cm in diameter with coatings optimized for use between 125-165 GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30 deg. with low cross-polarization. We describe the design, tolerance, manufacture, and measurements of these coatings and present measurements of the optical properties of silicon at millimeter wavelengths at cryogenic and room temperatures. This coating and lens fabrication approach is applicable from centimeter to sub-millimeter wavelengths and can be used to fabricate coatings with greater than octave bandwidth.

  17. Large-aperture Wide-bandwidth Antireflection-coated Silicon Lenses for Millimeter Wavelengths

    Science.gov (United States)

    Datta, R.; Munson, C. D.; Niemack, M. D.; McMahon, J. J.; Britton, J.; Wollack, Edward J.; Beall, J.; Devlin, M. J.; Fowler, J.; Gallardo, P.; Hubmayr, J.; Irwin, K.; Newburgh, L.; Nibarger, J. P.; Page, L.; Quijada, Manuel A.; Schmitt, B. L.; Staggs, S. T.; Thornton, R.; Zhang, L.

    2013-01-01

    The increasing scale of cryogenic detector arrays for submillimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n 3.4, low loss, and high thermal conductivity is a nearly optimal material for these purposes but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coefficient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three-axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating.We have fabricated silicon lenses as large as 33.4 cm in diameter with micromachined layers optimized for use between 125 and 165 GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30deg with low cross polarization.We describe the design, tolerance, manufacture, and measurements of these coatings and present measurements of the optical properties of silicon at millimeter wavelengths at cryogenic and room temperatures. This coating and lens fabrication approach is applicable from centimeter to submillimeter wavelengths and can be used to fabricate coatings with greater than octave bandwidth.

  18. Sub-wavelength diffractive optics

    Energy Technology Data Exchange (ETDEWEB)

    Warren, M.E.; Wendt, J.R.; Vawter, G.A.

    1998-03-01

    This report represents the completion of a three-year Laboratory-Directed Research and Development (LDRD) program to investigate sub-wavelength surface relief structures fabricated by direct-write e-beam technology as unique and very high-efficiency optical elements. A semiconductor layer with sub-wavelength sized etched openings or features can be considered as a layer with an effective index of refraction determined by the fraction of the surface filled with semiconductor relative to the fraction filled with air or other material. Such as a layer can be used to implement planar gradient-index lenses on a surface. Additionally, the nanometer-scale surface structures have diffractive properties that allow the direct manipulation of polarization and altering of the reflective properties of surfaces. With this technology a single direct-write mask and etch can be used to integrate a wide variety of optical functions into a device surface with high efficiencies; allowing for example, direct integration of polarizing optics into the surface with high efficiencies; allowing for example, direct integration of polarizing optics into the surfaces of devices, forming anti-reflection surfaces or fabricating high-efficiency, high-numerical aperture lenses, including integration inside vertical semiconductor laser cavities.

  19. Compact silicon photonic wavelength-tunable laser diode with ultra-wide wavelength tuning range

    Energy Technology Data Exchange (ETDEWEB)

    Kita, Tomohiro, E-mail: tkita@ecei.tohoku.ac.jp; Tang, Rui; Yamada, Hirohito [Graduate School of Engineering, Tohoku University, 6-6-05 Aramaki-Aza-Aoba, Aoba-ku, Sendai 980-8579 (Japan)

    2015-03-16

    We present a wavelength-tunable laser diode with a 99-nm-wide wavelength tuning range. It has a compact wavelength-tunable filter with high wavelength selectivity fabricated using silicon photonics technology. The silicon photonic wavelength-tunable filter with wide wavelength tuning range was realized using two ring resonators and an asymmetric Mach-Zehnder interferometer. The wavelength-tunable laser diode fabricated by butt-joining a silicon photonic filter and semiconductor optical amplifier shows stable single-mode operation over a wide wavelength range.

  20. Compact silicon photonic wavelength-tunable laser diode with ultra-wide wavelength tuning range

    International Nuclear Information System (INIS)

    We present a wavelength-tunable laser diode with a 99-nm-wide wavelength tuning range. It has a compact wavelength-tunable filter with high wavelength selectivity fabricated using silicon photonics technology. The silicon photonic wavelength-tunable filter with wide wavelength tuning range was realized using two ring resonators and an asymmetric Mach-Zehnder interferometer. The wavelength-tunable laser diode fabricated by butt-joining a silicon photonic filter and semiconductor optical amplifier shows stable single-mode operation over a wide wavelength range

  1. Young Extragalactic Radio Sources

    CERN Document Server

    Snellen, I; Snellen, Ignas; Schilizzi, Richard

    1999-01-01

    Gigahertz Peaked Spectrum (GPS) sources and Compact Symmetric Objects (CSO) are selected in very different ways, but have a significant overlap in properties. Ever since their discovery it has been speculated that they are young objects, but only recently, strong evidence has been provided indicating that GPS sources and CSOs are indeed the young counterparts of large, extended sources. They are therefore the objects of choice to study the initial evolution of extragalactic radio sources. Observational constraints on the luminosity evolution of young radio sources have mainly come from number density statistics and source size distributions, indicating that young sources should decrease in luminosity by a factor ~10 as they evolve to extended objects. We argue that the growth or decay in radio power of the individual objects has a strong influence on the slope of their collective luminosity function. This has led to a new method of constraining the evolution of young sources by comparing their luminosity func...

  2. Radio emission from novae

    International Nuclear Information System (INIS)

    The nature and measurement of radio emission from novae is discussed. The classical novae for which there are reported measurements of radio flux densities are listed. The three which have been studied most extensively are the slow nova HR Delta, the moderate speed nova FH Ser and the fast nova V1500 Cyg. Two different types of models have been used to model classical novae, the variable speed model and a Hubble flow model. V1500 Cyg has been observed in both radio and infrared spectra. The behaviour which explains this is discussed. Estimates of distance shell, mass and kinetic energy have been made from the data. Radioemissions from related objects and nova remnants are also discussed. (U.K.)

  3. Radio structure in quasars

    International Nuclear Information System (INIS)

    In this thesis, observational attention is given to the extended extragalactic radio sources associated with quasars. The isolated compact radio sources, often identified with quasars, are only included in the discussions. Three aspects of the radio structure in quasars and their cosmic evolution are considered: a study of the parsec scale morphology in quasar cores, in relation to the extended morphologies; an investigation of possible epoch dependent hotspot properties as well as a more detailed investigation of this fine scale structure; a VLA project was carried out to obtain morphological information on scales of 0.5 arcsec on high redshift quasars and to investigate possible epoch dependent morphological properties. MERLIN observations at 0.1 arcsec resolution to supplement the VLA data were initiated. (Auth.)

  4. Multimoment Radio Transient Detection

    CERN Document Server

    Spitler, Laura; Chatterjee, Shami; Stone, Julia

    2011-01-01

    We present a multimoment technique for signal classification and apply it to the detection of fast radio transients in incoherently dedispersed data. Specifically, we define a spectral modulation index in terms of the fractional variation in intensity across a spectrum. A signal whose intensity is distributed evenly across the entire band has a much lower modulation index than a spectrum with the same intensity localized in a single channel. We are interested in broadband pulses and use the modulation index to excise narrowband radio frequency interference (RFI) by applying a modulation index threshold above which candidate events are removed. The technique is tested both with simulations and using data from sources of known radio pulses (RRAT J1928+15 and giant pulses from the Crab pulsar). We find that our technique is effective at eliminating not only narrowband RFI but also spurious signals from bright, real pulses that are dedispersed at incorrect dispersion measures. The method is generalized to coheren...

  5. Planetary radio waves

    Science.gov (United States)

    Goertz, C. K.

    1986-01-01

    Three planets, the earth, Jupiter and Saturn are known to emit nonthermal radio waves which require coherent radiation processes. The characteristic features (frequency spectrum, polarization, occurrence probability, radiation pattern) are discussed. Radiation which is externally controlled by the solar wind is distinguished from internally controlled radiation which only originates from Jupiter. The efficiency of the externally controlled radiation is roughly the same at all three planets (5 x 10 to the -6th) suggesting that similar processes are active there. The maser radiation mechanism for the generation of the radio waves and general requirements for the mechanism which couples the power generator to the region where the radio waves are generated are briefly discussed.

  6. Wavelength Shifters for Water Cherenkov Detectors

    OpenAIRE

    Dai, Xiongxin; Rollin, Etienne; Bellerive, Alain; Hargrove, Cliff; Sinclair, David; Mifflin, Cathy; Zhang, Feng

    2008-01-01

    The light yield of a water-based Cherenkov detector can be significantly improved by adding a wavelength shifter. Wavelength shifter (WLS) molecules absorb ultraviolet photons and re-emit them at longer wavelengths where typical photomultiplier tubes are more sensitive. In this study, several wavelength shifter compounds are tested for possible deployment in the Sudbury Neutrino Observatory (SNO). Test results on optical properties and chemical compatibility for a few WLS candidates are repor...

  7. Radio quiet, please! - protecting radio astronomy from interference

    CERN Document Server

    Van Driel, W

    2009-01-01

    The radio spectrum is a finite and increasingly precious resource for astronomical research, as well as for other spectrum users. Keeping the frequency bands used for radio astronomy as free as possible of unwanted Radio Frequency Interference (RFI) is crucial. The aim of spectrum management, one of the tools used towards achieving this goal, includes setting regulatory limits on RFI levels emitted by other spectrum users into the radio astronomy frequency bands. This involves discussions with regulatory bodies and other spectrum users at several levels - national, regional and worldwide. The global framework for spectrum management is set by the Radio Regulations of the International Telecommunication Union, which has defined that interference is detrimental to radio astronomy if it increases the uncertainty of a measurement by 10%. The Radio Regulations are revised every three to four years, a process in which four organisations representing the interests of the radio astronomical community in matters of sp...

  8. Mobile radio channels

    CERN Document Server

    Pätzold, Matthias

    2011-01-01

    Providing a comprehensive overview of the modelling, analysis and simulation of mobile radio channels, this book gives a detailed understanding of fundamental issues and examines state-of-the-art techniques in mobile radio channel modelling. It analyses several mobile fading channels, including terrestrial and satellite flat-fading channels, various types of wideband channels and advanced MIMO channels, providing a fundamental understanding of the issues currently being investigated in the field. Important classes of narrowband, wideband, and space-time wireless channels are explored in deta

  9. Radio Emission from Supernovae

    International Nuclear Information System (INIS)

    Study of radio supernovae over the past 27 years includes more than three dozen detected objects and more than 150 upper limits. From this work it is possible to identify classes of radio properties, demonstrate conformance to and deviations from existing models, estimate the density and structure of the circumstellar material and, by inference, the evolution of the presupernova stellar wind, and reveal the last stages of stellar evolution before explosion. It is also possible to detect ionized hydrogen along the line of sight, to demonstrate binary properties of the presupernova stellar system, and to detect dumpiness of the circumstellar material.

  10. The LOFAR radio environment

    OpenAIRE

    Offringa, A. R.; et al, .; Hessels, J.; Swinbank, J.; Leeuwen, van; Wijers, R. A. M. J.; Wise, M.

    2013-01-01

    Aims. This paper discusses the spectral occupancy for performing radio astronomy with the Low-Frequency Array (LOFAR), with a focus on imaging observations. Methods. We have analysed the radio-frequency interference (RFI) situation in two 24-h surveys with Dutch LOFAR stations, covering 30−78 MHz with low-band antennas and 115-163 MHz with high-band antennas. This is a subset of the full frequency range of LOFAR. The surveys have been observed with a 0.76 kHz/1 s resolution. Results. We measu...

  11. The LOFAR radio environment

    OpenAIRE

    Offringa, A. R.; De Bruyn, A. G.; Zaroubi, S.; Van Diepen, G.; Martinez-Ruby, O.; Labropoulos, P.; Brentjens, M. A.; Ciardi, B.; Daiboo, S.; Harker, G.; Jelic, V.; Kazemi, S; Koopmans, L. V. E.; Mellema, G.; Pandey, V. N.

    2012-01-01

    Aims: This paper discusses the spectral occupancy for performing radio astronomy with the Low-Frequency Array (LOFAR), with a focus on imaging observations. Methods: We have analysed the radio-frequency interference (RFI) situation in two 24-h surveys with Dutch LOFAR stations, covering 30-78 MHz with low-band antennas and 115-163 MHz with high-band antennas. This is a subset of the full frequency range of LOFAR. The surveys have been observed with a 0.76 kHz / 1 s resolution. Results: We mea...

  12. Panoramic Radio Astronomy

    OpenAIRE

    Heald, G.; P. Serra

    2009-01-01

    In this contribution we give a brief overview of the Panoramic Radio Astronomy (PRA) conference held on 2-5 June 2009 in Groningen, the Netherlands. The conference was motivated by the on-going development of a large number of new radio telescopes and instruments which, within a few years, will bring a major improvement over current facilities. Interferometers such as the EVLA, ASKAP, ATA, MeerKAT, and APERTIF will provide a combination of larger field of view and increased simultaneous bandw...

  13. Sub-microsecond wavelength stabilization of tunable lasers with the internal wavelength locker

    Science.gov (United States)

    Kimura, Ryoga; Tatsumoto, Yudai; Sakuma, Kazuki; Onji, Hirokazu; Shimokozono, Makoto; Ishii, Hiroyuki; Kato, Kazutoshi

    2016-08-01

    We proposed a method of accelerating the wavelength stabilization after wavelength switching of the tunable distributed amplification-distributed feedback (TDA-DFB) laser using the internal wavelength locker to reduce the size and the cost of the wavelength control system. The configuration of the wavelength stabilization system based on this locker was as follows. At the wavelength locker, the light intensity after an optical filter is detected as a current by the photodiodes (PDs). Then, for estimating the wavelength, the current is processed by the current/voltage-converting circuit (IVC), logarithm amplifier (Log Amp) and field programmable gate array (FPGA). Finally, the laser current is tuned to the desired wavelength with reference to the estimated wavelength. With this control system the wavelength is stabilized within 800 ns after wavelength switching, which is even faster than that with the conventional control system.

  14. Determining the radio AGN contribution to the radio-FIR correlation using the black hole fundamental plane relation

    CERN Document Server

    Wong, O Ivy; Schawinski, K; Kapińska, A D; Lamperti, I; Oh, K; Ricci, C; Berney, S

    2016-01-01

    We investigate the 1.4 GHz radio properties of 92 nearby (z<0.05) ultra hard X-ray selected Active Galactic Nuclei (AGN) from the Swift Burst Alert Telescope (BAT) sample. Through the ultra hard X-ray selection we minimise the biases against obscured or Compton-thick AGN as well as confusion with emission derived from star formation that typically affect AGN samples selected from the UV, optical and infrared wavelengths. We find that all the objects in our sample of nearby, ultra-hard X-ray selected AGN are radio quiet; 83\\% of the objects are classed as high-excitation galaxies (HEGs) and 17\\% as low-excitation galaxies (LEGs). While these low-z BAT sources follow the radio--far-infrared correlation in a similar fashion to star forming galaxies, our analysis finds that there is still significant AGN contribution in the observed radio emission from these radio quiet AGN. In fact, the majority of our BAT sample occupy the same X-ray--radio fundamental plane as have been observed in other samples, which incl...

  15. 75 FR 10439 - Cognitive Radio Technologies and Software Defined Radios

    Science.gov (United States)

    2010-03-08

    ... Order 1. On March 17, 2005, the Commission adopted the Cognitive Radio Report and Order, 70 FR 23032... COMMISSION 47 CFR Part 2 Cognitive Radio Technologies and Software Defined Radios AGENCY: Federal... Memorandum Opinion and Order (MO&O), 72 FR 31190, June 6, 2007, which responded to two petitions filed...

  16. A Reconfigurable Radio Architecture for Cognitive Radio in Emergency Networks

    NARCIS (Netherlands)

    Zhang, Qiwei; Kokkeler, Andre B.J.; Smit, Gerard J.M.

    2006-01-01

    Cognitive Radio has been proposed as a promising technology to solve today's spectrum scarcity problem. Cognitive Radio is able to sense the spectrum to find the free spectrum, which can be optimally used by Cognitive Radio without causing interference to the licensed user. In the scope of the Adapt

  17. Spectrum management and radio resource management considering cognitive radio systems

    NARCIS (Netherlands)

    Haartsen, Jaap C.; Wieweg, Lasse; Huschke, Jörg

    2005-01-01

    International fora and some national administrations define a cognitive radio (CR) as a pioneering radio communication system that would be capable of altering and adapting its transmitter and receiver parameters based on communication and the exchange of information with related detectable radio co

  18. Star formation in hosts of young radio galaxies

    OpenAIRE

    Labiano, A.; O'Dea, C. P.; Barthel, P. D.; W. H. De Vries; Baum, S. A.

    2005-01-01

    We present near ultraviolet imaging with the Hubble Space Telescope Advanced Camera for Surveys, targeting young radio galaxies (Gigahertz Peaked Spectrum and Compact Steep Spectrum sources), in search of star formation regions in their hosts. We find near UV light which could be the product of recent star formation in eight of the nine observed sources. However, observations at other wavelengths and colors are needed to definitively establish the nature of the observed UV light. In the CSS s...

  19. Radio-Optical Galaxy Shape Correlations in the COSMOS Field

    CERN Document Server

    Tunbridge, Ben; Brown, Michael L

    2016-01-01

    We investigate the correlations in galaxy shapes between optical and radio wavelengths using archival observations of the COSMOS field. Cross-correlation studies between different wavebands will become increasingly important for precision cosmology as future large surveys may be dominated by systematic rather than statistical errors. In the case of weak lensing, galaxy shapes must be measured to extraordinary accuracy (shear systematics of $ 0.212\\pi$ radians (or $38.2^{\\circ}$) at a $95\\%$ confidence level.

  20. Radio-over-Fiber Transmission Using Vortex Modes

    DEFF Research Database (Denmark)

    Tatarczak, Anna; Lu, Xiaofeng; Rommel, Simon;

    2015-01-01

    This paper demonstrates experimentally the distribution of radio-over-fiber (RoF) signals using orbital angular momentum (OAM) of light over standard OM4 multimode fiber (MMF) at 850 nm wavelength. Five independent OAM modes are used to convey RoF signals in the microwave regime showing robust...... performance and therefore opening new prospects for enhancing the capacity of MMF based RoF Links....

  1. New supernova remnants from deer radio continuum surveys

    International Nuclear Information System (INIS)

    Based on radio continuum surveys of the Galactic plane at wavelengths of 21 cm and 11 cm we have so far identified about 32 new supernova remnants in the area 357 degrees .4 ≤ l ≤ 76 degrees, |b| ≤ 5 degrees. This increases the number of known objects in this field by about 68%. Most of them are in the galactic latitude range |b| > 0 degrees.5. Some implications are discussed

  2. Prospects in the orbital and rotational dynamics of the Moon with the advent of sub-centimeter lunar laser ranging

    Science.gov (United States)

    Kopeikin, S. M.; Pavlis, E.; Pavlis, D.; Brumberg, V. A.; Escapa, A.; Getino, J.; Gusev, A.; Müller, J.; Ni, W.-T.; Petrova, N.

    2008-10-01

    Lunar laser ranging (LLR) measurements are crucial for advanced exploration of the laws of fundamental gravitational physics and geophysics as well as for future human and robotic missions to the Moon. The corner-cube reflectors (CCR) currently on the Moon require no power and still work perfectly since their installation during the project Apollo era. Current LLR technology allows us to measure distances to the Moon with a precision approaching 1 mm. As NASA pursues the vision of taking humans back to the Moon, new, more precise laser ranging applications will be demanded, including continuous tracking from more sites on Earth, placing new CCR arrays on the Moon, and possibly installing other devices such as transponders, etc. for multiple scientific and technical purposes. Since this effort involves humans in space, then in all situations the accuracy, fidelity, and robustness of the measurements, their adequate interpretation, and any products based on them, are of utmost importance. Successful achievement of this goal strongly demands further significant improvement of the theoretical model of the orbital and rotational dynamics of the Earth-Moon system. This model should inevitably be based on the theory of general relativity, fully incorporate the relevant geophysical processes, lunar librations, tides, and should rely upon the most recent standards and recommendations of the IAU for data analysis. This paper discusses methods and problems in developing such a mathematical model. The model will take into account all the classical and relativistic effects in the orbital and rotational motion of the Moon and Earth at the sub-centimeter level. The model is supposed to be implemented as a part of the computer code underlying NASA Goddard's orbital analysis and geophysical parameter estimation package GEODYN and the ephemeris package PMOE 2003 of the Purple Mountain Observatory. The new model will allow us to navigate a spacecraft precisely to a location on the

  3. Multi-Wavelength Studies on H2O Maser Host Galaxies

    Indian Academy of Sciences (India)

    J. S. Zhang; J. Wang

    2011-03-01

    H2O maser emissions have been found in external galaxies for more than 30 years. Main sciences associated with extragalactic H2O masers can be summarized roughly into three parts: maser emission itself, AGN sciences and cosmology exploration. Our work in this field focusses on two projects: X-ray data analysis of individual maser source using X-ray penetrability to explore maser host obscured AGN; multi-wavelength statistical properties of the whole published H2O maser sample. Here their nuclear radio properties were investigated in detail, based on their 6-cm and 20-cm radio observation data. Comparing the radio properties between maser-detected sources and non-detected sources at similar distance scale, we find that: (1) maser host galaxies tend to have higher nuclear radio luminosity; (2) the spectral index of both samples is comparable (∼ 0.6), within the error ranges. In addition, for AGN-maser sources, the isotropic maser luminosity tends to increase with rising radio luminosity. Thus we propose the nuclear radio luminosity as one good indicator for searching AGN-masers in the future.

  4. Peering through Jupiter’s clouds with radio spectral imaging

    Science.gov (United States)

    de Pater, Imke; Sault, R. J.; Butler, Bryan; DeBoer, David; Wong, Michael H.

    2016-06-01

    Radio wavelengths can probe altitudes in Jupiter’s atmosphere below its visible cloud layers. We used the Very Large Array to map this unexplored region down to ~8 bar, ~100 kilometers below the visible clouds. Our maps reveal a dynamically active planet at pressures less than 2 to 3 bar. A radio-hot belt exists, consisting of relatively transparent regions (a low ammonia concentration, NH3 being the dominant source of opacity) probing depths to over ~8 bar; these regions probably coincide with 5-micrometer hot spots. Just to the south we distinguish an equatorial wave, bringing up ammonia gas from Jupiter’s deep atmosphere. This wave has been theorized to produce the 5-micrometer hot spots; we observed the predicted radio counterpart of such hot spots.

  5. Advances in Astrometry and Geophysics Made Possible by Radio Interferometry

    Science.gov (United States)

    Johnston, Kenneth J.

    1998-01-01

    Radio Interferometry has had a tremendous impact on the development of astrometry and geodesy. Barry Clark has played a leading role in developing the technology of radio interferometry through his work on connected-element interferometry, i.e., the Green Bank Interferometer and Very Large Array; and VLBI, i.e., the Mark I and II VLBI systems and the Very Long Baseline Array (VLBA). These efforts resulted in an increase in astrometric accuracy of four orders of magnitude. Stellar positions at radio wavelengths now can be measured with a precision of 0.1 milliarcseconds (mas). Earth orientation parameters such as UT1 and polar motion are now measured with precisions of 10 microarcseconds (micronas). The precession constants and models for nutation need revision to precisions at the microarcsecond level. Tectonic plate motion was directly measured in the 1980s. These were and are exciting times for research in these fields and Barry's scientific career parallels them especially in astrometry.

  6. Detection of fast transients with radio interferometric arrays

    CERN Document Server

    Bhat, N D R; Cox, P J; Gupta, Y; Prasad, J; Roy, J; Bailes, M; Burke-Spolaor, S; Kudale, S S; van Straten, W

    2013-01-01

    Next-generation radio arrays, including the SKA and its pathfinders, will open up new avenues for exciting transient science at radio wavelengths. Their innovative designs, comprising a large number of small elements, pose several challenges in digital processing and optimal observing strategies. The Giant Metre-wave Radio Telescope (GMRT)presents an excellent test-bed for developing and validating suitable observing modes and strategies for transient experiments with future arrays. Here we describe the first phase of the ongoing development of a transient detection system for GMRT that is planned to eventually function in a commensal mode with other observing programs. It capitalizes on the GMRT's interferometric and sub-array capabilities, and the versatility of a new software backend. We outline considerations in the plan and design of transient exploration programs with interferometric arrays, and describe a pilot survey that was undertaken to aid in the development of algorithms and associated analysis s...

  7. Radio Counterparts of Compact Binary Mergers detectable in Gravitational Waves: A Simulation for an Optimized Survey

    OpenAIRE

    Hotokezaka, Kenta; Nissanke, Samaya; Hallinan, Gregg; Lazio, T. Joseph W.; Nakar, Ehud; Piran, Tsvi

    2016-01-01

    Mergers of binary neutron stars and black hole-neutron star binaries produce gravitational-wave (GW) emission and outflows with significant kinetic energies. These outflows result in radio emissions through synchrotron radiation of accelerated electrons in shocks formed with the circum-merger medium. We explore the detectability of these synchrotron generated radio signals by follow-up observations of GW merger events lacking a detection of electromagnetic counterparts in other wavelengths. W...

  8. A Dedicated Search for Low Frequency Radio Transient Astrophysical Events using ETA

    OpenAIRE

    Deshpande, Kshitija Bharat

    2009-01-01

    Astrophysical phenomena such as self-annihilation of primordial black holes (PBHs), gamma ray bursts (GRBs), and supernovae are expected to produce single dispersed pulses detectable in the low end of the radio spectrum. Analysis of these pulses could provide valuable information about the sources, and the surrounding and intervening medium. The Eight-meter-wavelength Transient Array (ETA) is a radio telescope dedicated to the search for these pulses in an 18 MHz bandwidth centered at 38 MHz....

  9. Shock Formation Height in the Solar Corona Estimated from SDO and Radio Observations

    Science.gov (United States)

    Gopalswamy, N.; Nitta, N.

    2011-01-01

    Wave transients at EUV wavelengths and type II radio bursts are good indicators of shock formation in the solar corona. We use recent EUV wave observations from SDO and combine them with metric type II radio data to estimate the height in the corona where the shocks form. We compare the results with those obtained from other methods. We also estimate the shock formation heights independently using white-light observations of coronal mass ejections that ultimately drive the shocks.

  10. RadioLensfit: Bayesian weak lensing measurement in the visibility domain

    OpenAIRE

    Rivi, Marzia; Miller, Lance,; Makhathini, Sphesihle; Abdalla, Filipe Batoni

    2016-01-01

    Observationally, weak lensing has been served so far by optical surveys due to the much larger number densities of background galaxies achieved, which is typically by two to three orders of magnitude compared to radio. However, the high sensitivity of the new generation of radio telescopes such as the Square Kilometre Array (SKA) will provide a density of detected galaxies that is comparable to that found at optical wavelengths, and with significant source shape measurements to make large are...

  11. Software Defined Radio Transceiver Implementation

    OpenAIRE

    Corley, Gerry; Sanchez Mora , Magdalena; Farrell, Ronan

    2008-01-01

    This document presents the design and implementation of a low cost reconfigurable radio transceiver platform. The platform will be used as a research tool in the investigation of software defined radio techniques. The hardware presented is an evolution of work presented at the 2006 RIA colloquium. The platform consists of four hardware elements, namely a radio transmitter, a radio receiver, a baseband interface and a PC to perform signal processing and configuration. Data and control c...

  12. Zelenchukskaya Radio Astronomical Observatory

    Science.gov (United States)

    Smolentsev, Sergey; Dyakov, Andrei

    2013-01-01

    This report summarizes information about Zelenchukskaya Radio Astronomical Observatory activities in 2012. Last year a number of changes took place in the observatory to improve some technical characteristics and to upgrade some units to the required status. The report provides an overview of current geodetic VLBI activities and gives an outlook for the future.

  13. Svetloe Radio Astronomical Observatory

    Science.gov (United States)

    Smolentsev, Sergey; Rahimov, Ismail

    2013-01-01

    This report summarizes information about the Svetloe Radio Astronomical Observatory activities in 2012. Last year, a number of changes took place in the observatory to improve some technical characteristics and to upgrade some units to their required status. The report provides an overview of current geodetic VLBI activities and gives an outlook for the future.

  14. The LOFAR radio environment

    CERN Document Server

    Offringa, A R; Zaroubi, S; van Diepen, G; Martinez-Ruby, O; Labropoulos, P; Brentjens, M A; Ciardi, B; Daiboo, S; Harker, G; Jelic, V; Kazemi, S; Koopmans, L V E; Mellema, G; Pandey, V N; Pizzo, R F; Schaye, J; Vedantham, H; Veligatla, V; Wijnholds, S J; Yatawatta, S; Zarka, P; Alexov, A; Anderson, J; Asgekar, A; Avruch, M; Beck, R; Bell, M; Bell, M R; Bentum, M; Bernardi, G; Best, P; Birzan, L; Bonafede, A; Breitling, F; Broderick, J W; Bruggen, M; Butcher, H; Conway, J; de Vos, M; Dettmar, R J; Eisloeffel, J; Falcke, H; Fender, R; Frieswijk, W; Gerbers, M; Griessmeier, J M; Gunst, A W; Hassall, T E; Heald, G; Hessels, J; Hoeft, M; Horneffer, A; Karastergiou, A; Kondratiev, V; Koopman, Y; Kuniyoshi, M; Kuper, G; Maat, P; Mann, G; McKean, J; Meulman, H; Mevius, M; Mol, J D; Nijboer, R; Noordam, J; Norden, M; Paas, H; Pandey, M; Pizzo, R; Polatidis, A; Rafferty, D; Rawlings, S; Reich, W; Rottgering, H J A; Schoenmakers, A P; Sluman, J; Smirnov, O; Sobey, C; Stappers, B; Steinmetz, M; Swinbank, J; Tagger, M; Tang, Y; Tasse, C; van Ardenne, A; van Cappellen, W; van Duin, A P; van Haarlem, M; van Leeuwen, J; van Weeren, R J; Vermeulen, R; Vocks, C; Wijers, R A M J; Wise, M; Wucknitz, O

    2012-01-01

    Aims: This paper discusses the spectral occupancy for performing radio astronomy with the Low-Frequency Array (LOFAR), with a focus on imaging observations. Methods: We have analysed the radio-frequency interference (RFI) situation in two 24-h surveys with Dutch LOFAR stations, covering 30-78 MHz with low-band antennas and 115-163 MHz with high-band antennas. This is a subset of the full frequency range of LOFAR. The surveys have been observed with a 0.76 kHz / 1 s resolution. Results: We measured the RFI occupancy in the low and high frequency sets to be 1.8% and 3.2% respectively. These values are found to be representative values for the LOFAR radio environment. Between day and night, there is no significant difference in the radio environment. We find that lowering the current observational time and frequency resolutions of LOFAR results in a slight loss of flagging accuracy. At LOFAR's nominal resolution of 0.76 kHz and 1 s, the false-positives rate is about 0.5%. This rate increases approximately linear...

  15. Albanian: Basic Radio Communications.

    Science.gov (United States)

    Defense Language Inst., Washington, DC.

    This volume has been designed as a supplement to a course in Albanian developed by the Defense Language Institute. The emphasis in this text is placed on radio communications instruction. The volume is divided into five exercises, each of which contains a vocabulary, dictation, and an air-to-ground communications procedure conducted in Albanian…

  16. Optimized wavelength selection for molecular absorption thermometry.

    Science.gov (United States)

    An, Xinliang; Caswell, Andrew W; Lipor, John J; Sanders, Scott T

    2015-04-01

    A differential evolution (DE) algorithm is applied to a recently developed spectroscopic objective function to select wavelengths that optimize the temperature precision of water absorption thermometry. DE reliably finds optima even when many-wavelength sets are chosen from large populations of wavelengths (here 120 000 wavelengths from a spectrum with 0.002 cm(-1) resolution calculated by 16 856 transitions). Here, we study sets of fixed wavelengths in the 7280-7520 cm(-1) range. When optimizing the thermometer for performance within a narrow temperature range, the results confirm that the best temperature precision is obtained if all the available measurement time is split judiciously between the two most temperature-sensitive wavelengths. In the wide temperature range case (thermometer must perform throughout 280-2800 K), we find (1) the best four-wavelength set outperforms the best two-wavelength set by an average factor of 2, and (2) a complete spectrum (all 120 000 wavelengths from 16 856 transitions) is 4.3 times worse than the best two-wavelength set. Key implications for sensor designers include: (1) from the perspective of spectroscopic temperature sensitivity, it is usually sufficient to monitor two or three wavelengths, depending on the sensor's anticipated operating temperature range; and (2) although there is a temperature precision penalty to monitoring a complete spectrum, that penalty may be small enough, particularly at elevated pressure, to justify the complete-spectrum approach in many applications. PMID:25909716

  17. New Measurements of the Radio Photosphere of Mira Based on Data from the JVLA and ALMA

    Science.gov (United States)

    Matthews, L. D.; Reid, M. J.; Menten, K. M.

    2015-07-01

    We present new measurements of the millimeter wavelength continuum emission from the long period variable Mira (o Ceti) at frequencies of 46, 96, and 229 GHz (λ ≈ 7, 3, and 1 mm) based on observations obtained with the Jansky Very Large Array (JVLA) and the Atacama Large Millimeter/submillimeter Array (ALMA). The measured millimeter flux densities are consistent with a radio photosphere model derived from previous observations, where flux density {S}ν \\propto {ν }1.86. The stellar disk is resolved, and the measurements indicate a decrease in the size of the radio photosphere at higher frequencies, as expected if the opacity decreases at shorter wavelengths. The shape of the radio photosphere is found to be slightly elongated, with a flattening of ˜10%-20%. The data also reveal evidence for brightness non-uniformities on the surface of Mira at radio wavelengths. Mira’s hot companion, Mira B was detected at all three observed wavelengths, and we measure a radius for its radio-emitting surface of ≈ 2.0× {10}13 cm. The data presented here highlight the power of the JVLA and ALMA for the study of the atmospheres of evolved stars.

  18. Overview of an extensive multi-wavelength study of GX 339-4 during the 2010 outburst

    NARCIS (Netherlands)

    M. Cadolle Bel; J. Rodriguez; P. D'Avanzo; D.M. Russell; J. Tomsick; S. Corbel; F. W. Lewis; F. Rahoui; M. Buxton; P. Goldoni; E. Kuulkers

    2011-01-01

    Context. The microquasar GX 339−4 experienced a new outburst in 2010: it was observed simultaneously at various wavelengths from radio up to soft γ-rays. We focus on observations that are quasi-simultaneous with those made with the INTEGRAL and RXTE satellites: these were collected in 2010 March-Apr

  19. Multi-wavelength interferometry of evolved stars using VLTI and VLBA

    OpenAIRE

    Wittkowski, M.; Boboltz, D. A.; Driebe, T.; Ohnaka, K.

    2005-01-01

    We report on our project of coordinated VLTI/VLBA observations of the atmospheres and circumstellar environments of evolved stars. We illustrate in general the potential of interferometric measurements to study stellar atmospheres and envelopes, and demonstrate in particular the advantages of a coordinated multi-wavelength approach including near/mid-infrared as well as radio interferometry. We have so far made use of VLTI observations of the near- and mid-infrared stellar sizes and of concur...

  20. Wavelength Control of VCSEL Laser Employed in the Absolute Laser Interferometer

    Czech Academy of Sciences Publication Activity Database

    Mikel, Břetislav; Číp, Ondřej; Lazar, Josef

    Gent : URSI, 2005, D07b.7:1-4. ISSN 0074-9516. [General Assembly of International Union of Radio Science /28./. New Delhi (IN), 23.09.2005-29.09.2005] R&D Projects: GA AV ČR(CZ) KJB200650503 Institutional research plan: CEZ:AV0Z20650511 Keywords : wavelength-scanning interferometry * absolute interferometry * tunable laser * scale linearity Subject RIV: BH - Optics, Masers, Lasers

  1. Music Radio and Changes in a Morning Radio Show

    DEFF Research Database (Denmark)

    Have, Iben

    2016-01-01

    content of the programs (qualitatively as well as quantitatively) to an increasing emphasis on spoken words and entertaining hosts. The analysis as well as music radio more broadly are discussed in relation to the increasing competition with the global music streaming services and the general development......The article investigates the interdependency between music and radio through the concept of music radio in broadcast public service radio. A case study of a Danish morning music radio show during a period of 25 years illustrates a change of focus in this format from music being the most important...

  2. Are Cluster Radio Relics Revived Fossil Radio Cocoons?

    OpenAIRE

    Ensslin, Torsten A.; Gopal-Krishna

    2000-01-01

    A new model for the, so called, `cluster radio relics' is presented (Ensslin & Gopal-Krishna 2000). Fossil radio cocoons, resulting from the former activity of radio galaxies, should contain a low energy relativistic electron population and magnetic fields. Electrons with an age of even up to 2 Gyr can be re-accelerated adiabatically to radio emitting energies, if the fossil radio plasma gets compressed in an environmental shock wave. Such a wave can be caused by a merging event of galaxy clu...

  3. Width of Radio-Loud and Radio-Quiet CMEs

    OpenAIRE

    Michalek, G.; Gopalswamy, N.; Xie, H.

    2007-01-01

    In the present paper we report on the difference in angular sizes between radio-loud and radio-quiet CMEs. For this purpose we compiled these two samples of events using Wind/WAVES and SOHO/LASCO observations obtained during 1996-2005. It is shown that the radio-loud CMEs are almost two times wider than the radio-quiet CMEs (considering expanding parts of CMEs). Furthermore we show that the radio-quiet CMEs have a narrow expanding bright part with a large extended diffusive structure. These r...

  4. Radio Plasma as a Cosmological Probe

    OpenAIRE

    Ensslin, Torsten A.

    2001-01-01

    Plasma containing relativistic particles appears in various forms in the inter galactic medium (IGM): As radio plasma released by active radio galaxies, as fossil radio plasma from former radio galaxies - so called `radio ghosts', as `cluster radio relics' in some clusters of galaxies, and as `cluster radio halos'. The impact of the different forms of radio plasma on the IGM and their use as diagnostic tools are briefly discussed.

  5. The LOFAR radio environment

    Science.gov (United States)

    Offringa, A. R.; de Bruyn, A. G.; Zaroubi, S.; van Diepen, G.; Martinez-Ruby, O.; Labropoulos, P.; Brentjens, M. A.; Ciardi, B.; Daiboo, S.; Harker, G.; Jelić, V.; Kazemi, S.; Koopmans, L. V. E.; Mellema, G.; Pandey, V. N.; Pizzo, R. F.; Schaye, J.; Vedantham, H.; Veligatla, V.; Wijnholds, S. J.; Yatawatta, S.; Zarka, P.; Alexov, A.; Anderson, J.; Asgekar, A.; Avruch, M.; Beck, R.; Bell, M.; Bell, M. R.; Bentum, M.; Bernardi, G.; Best, P.; Birzan, L.; Bonafede, A.; Breitling, F.; Broderick, J. W.; Brüggen, M.; Butcher, H.; Conway, J.; de Vos, M.; Dettmar, R. J.; Eisloeffel, J.; Falcke, H.; Fender, R.; Frieswijk, W.; Gerbers, M.; Griessmeier, J. M.; Gunst, A. W.; Hassall, T. E.; Heald, G.; Hessels, J.; Hoeft, M.; Horneffer, A.; Karastergiou, A.; Kondratiev, V.; Koopman, Y.; Kuniyoshi, M.; Kuper, G.; Maat, P.; Mann, G.; McKean, J.; Meulman, H.; Mevius, M.; Mol, J. D.; Nijboer, R.; Noordam, J.; Norden, M.; Paas, H.; Pandey, M.; Pizzo, R.; Polatidis, A.; Rafferty, D.; Rawlings, S.; Reich, W.; Röttgering, H. J. A.; Schoenmakers, A. P.; Sluman, J.; Smirnov, O.; Sobey, C.; Stappers, B.; Steinmetz, M.; Swinbank, J.; Tagger, M.; Tang, Y.; Tasse, C.; van Ardenne, A.; van Cappellen, W.; van Duin, A. P.; van Haarlem, M.; van Leeuwen, J.; van Weeren, R. J.; Vermeulen, R.; Vocks, C.; Wijers, R. A. M. J.; Wise, M.; Wucknitz, O.

    2013-01-01

    Aims: This paper discusses the spectral occupancy for performing radio astronomy with the Low-Frequency Array (LOFAR), with a focus on imaging observations. Methods: We have analysed the radio-frequency interference (RFI) situation in two 24-h surveys with Dutch LOFAR stations, covering 30-78 MHz with low-band antennas and 115-163 MHz with high-band antennas. This is a subset of the full frequency range of LOFAR. The surveys have been observed with a 0.76 kHz/1 s resolution. Results: We measured the RFI occupancy in the low and high frequency sets to be 1.8% and 3.2% respectively. These values are found to be representative values for the LOFAR radio environment. Between day and night, there is no significant difference in the radio environment. We find that lowering the current observational time and frequency resolutions of LOFAR results in a slight loss of flagging accuracy. At LOFAR's nominal resolution of 0.76 kHz and 1 s, the false-positives rate is about 0.5%. This rate increases approximately linearly when decreasing the data frequency resolution. Conclusions: Currently, by using an automated RFI detection strategy, the LOFAR radio environment poses no perceivable problems for sensitive observing. It remains to be seen if this is still true for very deep observations that integrate over tens of nights, but the situation looks promising. Reasons for the low impact of RFI are the high spectral and time resolution of LOFAR; accurate detection methods; strong filters and high receiver linearity; and the proximity of the antennas to the ground. We discuss some strategies that can be used once low-level RFI starts to become apparent. It is important that the frequency range of LOFAR remains free of broadband interference, such as DAB stations and windmills.

  6. Radio Spectral Evolution of an X-ray Poor Impulsive Solar Flare: Implications for Plasma Heating and Electron Acceleration

    CERN Document Server

    Bastian, T S; Gary, D E

    2007-01-01

    We present radio and X-ray observations of an impulsive solar flare that was moderately intense in microwaves, yet showed very meager EUV and X-ray emission. The flare occurred on 2001 Oct 24 and was well-observed at radio wavelengths by the Nobeyama Radioheliograph (NoRH), the Nobeyama Radio Polarimeters (NoRP), and by the Owens Valley Solar Array (OVSA). It was also observed in EUV and X-ray wavelength bands by the TRACE, GOES, and Yohkoh satellites. We find that the impulsive onset of the radio emission is progressively delayed with increasing frequency relative to the onset of hard X-ray emission. In contrast, the time of flux density maximum is progressively delayed with decreasing frequency. The decay phase is independent of radio frequency. The simple source morphology and the excellent spectral coverage at radio wavelengths allowed us to employ a nonlinear chi-squared minimization scheme to fit the time series of radio spectra to a source model that accounts for the observed radio emission in terms of...

  7. Fast Radio Bursts and Their Gamma-Ray or Radio Afterglows as Kerr–Newman Black Hole Binaries

    Science.gov (United States)

    Liu, Tong; Romero, Gustavo E.; Liu, Mo-Lin; Li, Ang

    2016-07-01

    Fast radio bursts (FRBs) are radio transients lasting only about a few milliseconds. They seem to occur at cosmological distances. We propose that these events can originate in the collapse of the magnetospheres of Kerr–Newman black holes (KNBHs). We show that the closed orbits of charged particles in the magnetospheres of these objects are unstable. After examining the dependencies on the specific charge of the particle and the spin and charge of the KNBH, we conclude that the resulting timescale and radiation mechanism fit well with extant observations of FRBs. Furthermore, we argue that the merger of a KNBH binary is a plausible central engine for the potential gamma-ray or radio afterglow following certain FRBs and can also account for gravitational wave (GW) events like GW 150914. Our model leads to predictions that can be tested by combined multi-wavelength electromagnetic and GW observations.

  8. Clear sky atmosphere at cm-wavelengths from climatology data

    CERN Document Server

    Lew, Bartosz

    2015-01-01

    We utilise ground-based, balloon-born and satellite climatology data to reconstruct site and season-dependent vertical profiles of precipitable water vapour (PWV). We use these profiles to numerically solve radiative transfer through the atmosphere, and derive atmospheric brightness temperature ($T_{\\rm atm}$) and optical depth ($\\tau$) at the centimetre wavelengths. We validate the reconstruction by comparing the model column PWV, with photometric measurements of PWV, performed in the clear sky conditions towards the Sun. Based on the measurements, we devise a selection criteria to filter the climatology data to match the PWV levels to the expectations of the clear sky conditions. We apply the reconstruction to the location of the Polish 32-metre radio telescope, and characterise $T_{\\rm atm}$ and $\\tau$ year-round, at selected frequencies. We also derive the zenith distance dependence for these parameters, and discuss shortcomings of using planar, single-layer, and optically thin atmospheric model approxima...

  9. The radio structure of radio-quiet quasars

    CERN Document Server

    Leipski, C; Bennert, N; Hüttemeister, S; Leipski, Christian; Falcke, Heino; Bennert, Nicola; Huettemeister, Susanne

    2006-01-01

    We investigate the radio emitting structures of radio-quiet active galactic nuclei with an emphasis on radio-quiet quasars to study their connection to Seyfert galaxies. We present and analyse high-sensitivity VLA radio continuum images of 14 radio-quiet quasars and six Seyfert galaxies. Many of the low redshift radio-quiet quasars show radio structures that can be interpreted as jet-like outflows. However, the detection rate of extended radio structures on arcsecond scales among our sample decreases with increasing redshift and luminosity, most likely due to a lack of resolution. The morphologies of the detected radio emission indicate strong interactions of the jets with the surrounding medium. We also compare the radio data of seven quasars with corresponding HST images of the [OIII] emitting narrow-line region (NLR). We find that the scenario of interaction between the radio jet and the NLR gas is confirmed in two sources by structures in the NLR gas distribution as previously known for Seyfert galaxies. ...

  10. Multi-wavelength constraints on cosmic-ray leptons in the Galaxy

    CERN Document Server

    Orlando, E; Moskalenko, I V; Dickinson, C; Digel, S; Jaffe, T R; Jóhannesson, G; Leahy, J P; Porter, T A; Vidal, M

    2015-01-01

    Cosmic rays (CRs) interact with the gas, the radiation field and the magnetic field in the Milky Way, producing diffuse emission from radio to gamma rays. Observations of this diffuse emission and comparison with detailed predictions are powerful tools to unveil the CR properties and to study CR propagation. We present various GALPROP CR propagation scenarios based on current CR measurements. The predicted synchrotron emission is compared to radio surveys, and synchrotron temperature maps from WMAP and Planck, while the predicted interstellar gamma-ray emission is compared to Fermi-LAT observations. We show how multi-wavelength observations of the Galactic diffuse emission can be used to help constrain the CR lepton spectrum and propagation. Finally we discuss how radio and microwave data could be used in understanding the diffuse Galactic gamma-ray emission observed with Fermi-LAT, especially at low energies.

  11. Multi-wavelength polarimetry and variability study of M87 jet during 2002-2008

    Science.gov (United States)

    Avachat, Sayali S.; Perlman, Eric S.; Cara, Mihai; Owen, Frazer; Harris, Daniel E.; Sparks, William B.; Li, Kunyang; Kosak, Katie

    2016-01-01

    In this dissertation, we present the multi-wavelength study of M87 jet. We compare the radio and optical polarimetry and variability. We attempt to study the spectrum of the jet in radio through X-rays wavelengths. By comparing the data with previously published VLA and HST observations, we show that the jet's morphology in total and polarized light is changing significantly on timescales of ~1 decade. We are looking for the variability of different knots and changes in their spectra using our deep, high resolution observations of the jet between 2002 and 2008. The observations have 2-3 times better resolution that any similar previous study (Perlman et al. 1999) in addition allowing us to observe variability. During this time, the nucleus showed month-scale variability in optical and X-rays and also flared twice in all wave- lengths including radio. The knot HST-1, located closest to the nucleus, displayed a huge flare, increasing about 100 times in brightness. The knot A and B complex shows variations in polarization structures indicating the presence of a helical magnetic field which may be responsible for the in-situ particle accelerations in the jet. We compare the evolution of different knots and components of the jet, when our observations overlap with the multi-wavelength monitoring campaigns conducted with HST and Chandra and comment on particle acceleration and main emission processes. We further use the data to investigate the observed 3-dimensional structure of the jet and the magnetic field structure.

  12. Long wavelength quantum cascade lasers

    International Nuclear Information System (INIS)

    The aim of this work is the extension of the concept of quantum cascade lasers towards longer wavelengths and the exploration of quantum cascade emission in the terahertz frequency regime. The first step is the realization of quantum cascade lasers based on GaAs/AlGaAs chirped superlattice active regions with photon energies above the longitudinal optical (LO-) phonon energy. These lasers push the long wavelength limit of GaAs-based quantum cascade lasers (previously at 13) to 23 micrometers. The 23-micrometer device is the first GaAs based quantum cascade laser with a metal surface plasmon waveguide. This waveguide scheme allows a reduction of the thickness of the epitaxially grown layer system and is therefore appropriate for long wavelength lasers. The measured threshold current densities reflect the differences in intersubband lifetimes and waveguide losses close to the LO-phonon energy. The major part of this thesis is devoted to the terahertz regime, i.e. the photon energy range below the LO-phonon energy. The intersubband scattering rate is no longer governed by LO-phonon emission from electrons at zero in-plane momentum, but disorder related scattering and electron-electron scattering come into play. Terahertz quantum cascade structures are designed, fabricated, and experimentally examined. Narrow linewidth (1.3 millielectronvolts) spontaneous emission is detected at a photon energy of 17.3 millielectronvolts (λ = 72 micrometers). To achieve population inversion the intersubband scattering rates have to be carefully engineered. Three strategies to manipulate the non-radiative rate are demonstrated: (1) Magnetic field quantization of the electronic motion reduces non-radiative scattering. Magneto-intersubband oscillations caused by inter-Landau-level transitions allow to determine the optical transition energy independently of the emission. (2) A reduction of the spatial overlap of initial and final subband by a barrier in an interwell transition causes a

  13. Multi-wavelength INTEGRAL NEtwork (MINE) observations of the microquasar GRS 1915+105

    CERN Document Server

    Fuchs, Y; Shaw, S E; Kretschmar, P; Ribó, M; Chaty, S; Mirabel, I F; Dhawan, V; Pooley, G G; Brown, I; Spencer, R; Hannikainen, D C

    2004-01-01

    We present the international collaboration MINE (Multi-lambda Integral NEtwork) aimed at conducting multi-wavelength observations of X-ray binaries and microquasars simultaneously with the INTEGRAL gamma-ray satellite. We will focus on the 2003 March-April campaign of observations of the peculiar microquasar GRS 1915+105 gathering radio, IR and X-ray data. The source was observed 3 times in the plateau state, before and after a major radio and X-ray flare. It showed strong steady optically thick radio emission corresponding to powerful compact jets resolved in the radio images, bright near-infrared emission, a strong QPO at 2.5 Hz in the X-rays and a power law dominated spectrum without cutoff in the 3-300 keV range. We compare the different observations, their multi-wavelength light curves, including JEM-X, ISGRI and SPI, and the parameters deduced from fitting the spectra obtained with these instruments on board INTEGRAL.

  14. Arcsecond Resolution at 4 Meters Wavelength: The 74 MHz Band on the Very Large Array

    Science.gov (United States)

    Perley, R. A.

    2001-12-01

    Although the foundations of interferometric imaging were developed with instruments operating at meter wavelengths, most of the development of the techniques, and the subsequent science, have been done at increasingly shorter wavelengths. Two of the key reasons for the lack of a high-resolution imaging capability at meter wavelengths are the extreme difficulties in correcting for ionospheric phase corruption, and the complication and expense of image formation from the non-coplanar data taken by the Very Large Array. However, the techniques of self-calibration and image formation which have been developed for interferometry at shorter wavelengths can be modified and extended to handle the more difficult problems posed by long-wavelength, long-baseline interferometry. The differences between long- and short-wavelength imaging are only a matter of degree, not of principle. To test these techniques, and to demonstrate the potential of arcsecond resolution imaging at meter wavelengths, the Naval Research Laboratory and the National Radio Astronomy Observatory have outfitted the Very Large Array with receivers operating at a wavelength of 4 meters. Extensive tests with this new capability have shown that even simple extensions of the self-calibration methods developed for higher frequency data are sufficient to permit good imaging at this very long wavelength. More sophisticated variants of these techniques are now under development, and will soon allow full phase correction over the entire eleven-degree primary beam at the VLA's full resolution of 25 arcseconds. In addition, modern computers have provided the necessary capability to permit development of sophisticated, multi-faceted imaging techniques, allowing full primary beam imaging while avoiding the aberrations which accompany simple two-dimensional inversion of non-coplanar visibility data. Thus, both historical limitations have been bypassed, and true diffraction-limited, wide-field imaging at meter wavelengths

  15. Introduction to international radio regulations

    International Nuclear Information System (INIS)

    These lecture notes contain an overview of basic problems of the International Radio Regulations. Access to the existing information infrastructure, and to that of the future Information Society, depends critically on radio, especially in poor, remote and sparsely populated regions with under-developed telecommunication infrastructure. How the spectrum of radio frequencies is regulated has profound impact on the society, its security, prosperity, and culture. The radio regulations represent a very important framework for an adequate use of radio and should be known by all of those working in the field

  16. High frequency ion sound waves associated with Langmuir waves in type III radio burst source regions

    OpenAIRE

    G. Thejappa; Macdowall, R. J.

    2004-01-01

    Short wavelength ion sound waves (2-4kHz) are detected in association with the Langmuir waves (~15-30kHz) in the source regions of several local type III radio bursts. They are most probably not due to any resonant wave-wave interactions such as the electrostatic decay instability because their wavelengths are much shorter than those of Langmuir waves. The Langmuir waves occur as coherent field structures with peak intensities exceeding the Langm...

  17. JVLA Observations of IC 348SW: Compact Radio Sources and their Nature

    OpenAIRE

    Rodriguez, L. F.; L. A. Zapata; Palau, A.

    2014-01-01

    We present sensitive 2.1 and 3.3 cm JVLA radio continuum observations of the region IC 348 SW. We detect a total of 10 compact radio sources in the region, of which seven are first reported here. One of the sources is associated with the remarkable periodic time-variable infrared source LRLL 54361, opening the possibility of monitoring this object at radio wavelengths. Four of the sources appear to be powering outflows in the region, including HH 211 and HH 797. In the case of the rotating ou...

  18. Shock-related radio emission during coronal mass ejection lift-off?

    OpenAIRE

    Pohjolainen, S.

    2008-01-01

    Aims: We identify the source of fast-drifting decimetric-metric radio emission that is sometimes observed prior to the so-called flare continuum emission. Fast-drift structures and continuum bursts are also observed in association with coronal mass ejections (CMEs), not only flares. Methods: We analyse radio spectral features and images acquired at radio, H-alpha, EUV, and soft X-ray wavelengths, during an event close to the solar limb on 2 June 2003. Results: The fast-drifting decimetric-met...

  19. Measuring centimeter-resolution air temperature profiles above land and water using fiber-optic Distributed Temperature Sensing

    Science.gov (United States)

    Sigmund, Armin; Pfister, Lena; Olesch, Johannes; Thomas, Christoph K.

    2016-04-01

    The precise determination of near-surface air temperature profiles is of special importance for the characterization of airflows (e.g. cold air) and the quantification of sensible heat fluxes according to the flux-gradient similarity approach. In contrast to conventional multi-sensor techniques, measuring temperature profiles using fiber-optic Distributed Temperature Sensing (DTS) provides thousands of measurements referenced to a single calibration standard at much reduced costs. The aim of this work was to enhance the vertical resolution of Raman scatter DTS measurements up to the centimeter-scale using a novel approach for atmospheric applications: the optical fiber was helically coiled around a meshed fabric. In addition to testing the new fiber geometry, we quantified the measurement uncertainty and demonstrated the benefits of the enhanced-resolution profiles. The fiber-optic cable was coiled around a hollow column consisting of white reinforcing fabric supported by plexiglass rings every meter. Data from two columns of this type were collected for 47 days to measure air temperature vertically over 3.0 and 5.1 m over a gently inclined meadow and over and in a small lake, respectively. Both profiles had a vertical resolution of 1 cm in the lower section near the surface and 5 cm in the upper section with an along-fiber instrument-specific averaging of 1.0 m and a temporal resolution of 30 s. Measurement uncertainties, especially from conduction between reinforcing fabric and fiber-optic cable, were estimated by modeling the fiber temperature via a detailed energy balance approach. Air temperature, wind velocity and radiation components were needed as input data and measured separately. The temperature profiles revealed valuable details, especially in the lowest 1 m above surface. This was best demonstrated for nighttime observations when artefacts due to solar heating did not occur. For example, the dynamics of a cold air layer was detected in a clear night

  20. BOLOMETRIC ARRAYS FOR MILLIMETER WAVELENGTHS

    Directory of Open Access Journals (Sweden)

    E. Castillo

    2009-01-01

    Full Text Available During last years, semiconductor bolometers using thin lms have been developed at INAOE, speci cally boron-doped hydrogenated amorphous silicon lms. The characteristics shown by these devices made them attractive to be used in astronomical instrumentation, mainly in two-dimentional arrays. These detector arrays used at the Large Millimeter Telescope will make possible to obtain astronomical images in millimeter and submillimeter wavelengths. With this in mind, we are developing a method to produce, with enough reliability, bolometer arrays at INAOE. Until now, silicon nitride diaphragm arrays, useful as radiation absorbers, have succesfully been obtained. Sizes going from one to four millimeter by element in a consistent way; however we have not tested thermometers and metallic contact deposition yet. At the same time, we are working on two possible con gurations for the readout electronics; one of them using commercial components while the other will be an integrated circuit speci cally designed for this application. Both versions will work below 77K.

  1. Weak and Compact Radio Emission in Early High-Mass Star Forming Regions: I. VLA Observations

    CERN Document Server

    Rosero, V; Claussen, M; Kurtz, S; Cesaroni, R; Araya, E D; Carrasco-González, C; Rodríguez, L F; Menten, K M; Wyrowski, F; Loinard, L; Ellingsen, S P

    2016-01-01

    We present a high sensitivity radio continuum survey at 6 and 1.3$\\,$cm using the Karl G. Jansky Very Large Array towards a sample of 58 high-mass star forming regions. Our sample was chosen from dust clumps within infrared dark clouds with and without IR sources (CMC-IRs, CMCs, respectively), and hot molecular cores (HMCs), with no previous, or relatively weak radio continuum detection at the $1\\,$mJy level. Due to the improvement in the continuum sensitivity of the VLA, this survey achieved map rms levels of $\\sim$ 3-10 $\\mu$Jy beam$^{-1}$ at sub-arcsecond angular resolution. We extracted 70 centimeter continuum sources associated with 1.2$\\,$mm dust clumps. Most sources are weak, compact, and are prime candidates for high-mass protostars. Detection rates of radio sources associated with the mm dust clumps for CMCs, CMC-IRs and HMCs are 6$\\%$, 53$\\%$ and 100$\\%$, respectively. This result is consistent with increasing high-mass star formation activity from CMCs to HMCs. The radio sources located within HMCs...

  2. [Radio-guided parathyroidectomy].

    Science.gov (United States)

    Calbo, L; Gorgone, S; Palmieri, R; Lazzara, S; Sciglitano, P; Catalfamo, A; Calbo, E; Campennì, A; Ruggeri, M; Vermiglio, F; Baldari, S

    2009-01-01

    The Authors, after a careful review of literature about the instrumental diagnostic techniques (with particular attention to the nuclear-medical ones) and the surgical therapy of parathyroid diseases, report their experience on the use of the radio-guided mininvasive surgery with MIBI and gamma-probe for intraoperative localization of pathological glands. Once exposed their experience, the Authors conclude asserting that this technique is fast, slightly invasive and expensive, and certainly useful for the detection of pathological or ectopic glands. It can be widely employed because, in comparison to its numerous advantages, such as the reduction of the operating time and of the hospital-stay, the greater radicality and the possibility to use mininvasive techniques, it does not present significant technical limitations and/or radio-protectionistic problems. PMID:20109383

  3. Searches for radio transients

    CERN Document Server

    Bhat, N D R

    2011-01-01

    Exploration of the transient Universe is an exciting and fast-emerging area within radio astronomy. Known transient phenomena range in time scales from sub-nanoseconds to years or longer, thus spanning a huge range in time domain and hinting a rich diversity in their underlying physical processes. Transient phenomena are likely locations of explosive or dynamic events and they offer tremendous potential to uncover new physics and astrophysics. A number of upcoming next-generation radio facilities and recent advances in computing and instrumentation have provided a much needed impetus for this field which has remained a relatively uncharted territory for the past several decades. In this paper we focus mainly on the class of phenomena that occur on very short time scales (i.e. from $\\sim$ milliseconds to $\\sim$ nanoseconds), known as {\\it fast transients}, the detections of which involve considerable signal processing and data management challenges, given the high time and frequency resolutions required in the...

  4. Radio over fiber systems

    OpenAIRE

    Ghafoor, Salman

    2012-01-01

    The three main types of Radio Over Fiber (ROF)communication systems, namely analogue ROF, baseband ROF and digitized ROF are investigated. Optical fibers are increasingly replacing copper wires. In long-haul, high-bit-rate communication systems optical fiber has already become the dominant mode of transmission due to its enormous bandwidth and low loss. ROF facilitate the seamless integration of optical and wireless communication systems. Since the RF spectrum is limited, wireless systems rel...

  5. Multimoment Radio Transient Detection

    OpenAIRE

    Spitler, Laura; Cordes, Jim; Chatterjee, Shami; Stone, Julia

    2011-01-01

    We present a multimoment technique for signal classification and apply it to the detection of fast radio transients in incoherently dedispersed data. Specifically, we define a spectral modulation index in terms of the fractional variation in intensity across a spectrum. A signal whose intensity is distributed evenly across the entire band has a much lower modulation index than a spectrum with the same intensity localized in a single channel. We are interested in broadband pulses and use the m...

  6. MUSIC RADIO-JOURNALISM

    OpenAIRE

    Dubovtceva Ludmila I.

    2014-01-01

    The article is based on years of practical experience, the author highlights the main radio genres in which music correspondent, music reviewer, music commentator, and music leading and a disc jockey work. Theoretical principles of their creative activities are analyzed in common journalistic genres, such as interview, reportage, talk show, live broadcast, radiofilm, as well as specialized genres like concert on demand and music competition. Journalist’ speech is seen as a logical element, th...

  7. Radio frequency ion source

    CERN Document Server

    Shen Guan Ren; Gao Fu; LiuNaiYi

    2001-01-01

    The study on Radio Frequency Ion Source is mainly introduced, which is used for CIAE 600kV ns Pulse Neutron Generator; and obtained result is also presented. The RF ion source consists of a diameter phi 25 mm, length 200 mm, coefficient of expansion =3.5 mA, beam current on target >=1.5 mA, beam spot =100 h.

  8. Radio data network

    OpenAIRE

    Ampliato Millan, Miguel

    2006-01-01

    Radio Data Network is the title of a product, a product that is the results of three years studying Telecommunications, and one more Electrical and Electronic engineering. I had pretended that the purpose was a mix of both degrees, studying Radiofrequency but at the same time using Electronic methods to create a device able to be developed in a real application. The application in question is in a zoo, it pretends to be a useful technology to control from one place the habit...

  9. Wavelength-doubling optical parametric oscillator

    Science.gov (United States)

    Armstrong, Darrell J.; Smith, Arlee V.

    2007-07-24

    A wavelength-doubling optical parametric oscillator (OPO) comprising a type II nonlinear optical medium for generating a pair of degenerate waves at twice a pump wavelength and a plurality of mirrors for rotating the polarization of one wave by 90 degrees to produce a wavelength-doubled beam with an increased output energy by coupling both of the degenerate waves out of the OPO cavity through the same output coupler following polarization rotation of one of the degenerate waves.

  10. All-optical wavelength-shifting technologies

    DEFF Research Database (Denmark)

    Jørgensen, Carsten; Mikkelsen, Benny; Danielsen, Søren Lykke;

    1995-01-01

    State-of-the-art results for interferometric wavelength converters for WDM fiber networks have been presented. The interferometric converters are capable of high speed (10 Gbit/s), polarisation and wavelength independent (within 30 nn) wavelength conversion. In addition they offer unique features...... such as extinction ratio improvement and spectral cleaning. The 1-dB input power dynamic range is around 4 dB but can be increased to 8 dB by a simple control scheme...

  11. Danmarks Radios stemmer

    DEFF Research Database (Denmark)

    Lawaetz, Anna

    kanalspeakerne kändisser, hvis fortalelser i æteren såvel som private gøren og laden blev fulgt nøje i dagspressen. Anna Lawaetz har med ph.d.-afhandlingen Danmarks Radios stemmer med udgangspunkt i kanalspeakerne på P1 i perioden 1925-2012 gennem empiriske studier kortlagt fortællingen om institutionens stemmer...... – nøje udvalgte ikke-fiktionsstemmer i Danmarks Radio igennem tiden. Samtidig har hun lavet en konkret analyse af stemmerne baseret på både akustiske målinger og kategorisering af oplevelsen af stemmerne. Fx taler kanalspeakerne på P1 i dag ikke hurtigere end tidligere, men pauserne er blevet kortere...... datamængder kræver udvikling af nye metoder. Den metodiske udvikling har her været baseret på optagelser af stemmer for at undersøge hvordan man videnskabeligt kan arbejde med optagelser af stemmer som mere end teksttransskriptioner inden for det kulturvidenskabelige felt med afsæt i Danmarks Radios...

  12. Panoramic Radio Astronomy

    CERN Document Server

    Heald, G

    2009-01-01

    In this contribution we give a brief overview of the Panoramic Radio Astronomy (PRA) conference held on 2-5 June 2009 in Groningen, the Netherlands. The conference was motivated by the on-going development of a large number of new radio telescopes and instruments which, within a few years, will bring a major improvement over current facilities. Interferometers such as the EVLA, ASKAP, ATA, MeerKAT, and APERTIF will provide a combination of larger field of view and increased simultaneous bandwidth, while maintaining good collecting area and angular resolution. They will achieve a survey speed 10-50 times larger at 1-2 GHz than the current possibilities, allowing for the first time optical-like all-sky extra-galactic surveys at these frequencies. Significant progress will be made in many fields of radio astronomy. In this conference we focused on research into the evolution of galaxies over the past few Gyr. In particular, wide-field observations at 1-2 GHz will provide an unprecedented panoramic view of the ga...

  13. Calibration of Multi-wavelength Raman Polarization Lidar

    Directory of Open Access Journals (Sweden)

    Wang Xuan

    2015-01-01

    Full Text Available The current high energy cosmic ray detection technology, including Cherenkov telescopes and fluorescence detector, is mainly limited by uncertainties in the determination of atmospheric parameters. LIDARs are currently the best suited technology to get atmospheric parameters for the atmosphere correction of high energy cosmic ray observatory data with one single instrument. A new Multi-wavelength Raman Polarization Lidar (AMPLE has been developed and introduced in this paper. In order to provide precise and accurate results, lidar system should be calibrated before using for atmosphere correction in cosmic rays observatory. The calibration methods and results of AMPLE have been presented, including overlap function calibration, multi-wavelength channel calibration, depolarization calibration. In order to verify the accuracy of parameter measured by AMPLE lidar system, the comparison with radio sounder and sun-photometer has been done. The results show AMPLE lidar system has the ability to precisely measure the vertical profile of the atmosphere properties without any assumption and is a good choice for cosmic rays observatory to get atmosphere correction information.

  14. Wavelength-extended photovoltaic infrared photodetectors

    OpenAIRE

    Lao, Yan-Feng; Pitigala, P. K. D. D. P.; Unil Perera, A. G.; Li, L. H.; Khanna, S. P.; Linfield, E. H.

    2014-01-01

    We report the incorporation of a long-wavelength photovoltaic response (up to 8μm) in a short-wavelength p-type GaAs heterojunction detector (with the activation energy of EA∼0.40 eV), operating at 80K. This wavelength-extended photovoltaic response is enabled by employing a non-symmetrical band alignment. The specific detectivity at 5μm is obtained to be 3.5×10 cm Hz/W, an improvement by a factor of 10 over the detector without the wavelength extension.

  15. Optimizing constant wavelength neutron powder diffractometers

    Science.gov (United States)

    Cussen, Leo D.

    2016-06-01

    This article describes an analytic method to optimize constant wavelength neutron powder diffractometers. It recasts the accepted mathematical description of resolution and intensity in terms of new variables and includes terms for vertical divergence, wavelength and some sample scattering effects. An undetermined multiplier method is applied to the revised equations to minimize the RMS value of resolution width at constant intensity and fixed wavelength. A new understanding of primary spectrometer transmission (presented elsewhere) can then be applied to choose beam elements to deliver an optimum instrument. Numerical methods can then be applied to choose the best wavelength.

  16. HELP : The Herschel Extragalactic Legacy Project & The Coming of Age of Multi-Wavelength Astrophysics

    CERN Document Server

    Vaccari, Mattia

    2015-01-01

    How did galaxies form and evolve? This is one of the most challenging questions in astronomy today. Answering it requires a careful combination of observational and theoretical work to reliably determine the observed properties of cosmic bodies over large portions of the distant Universe on the one hand, and accurately model the physical processes driving their evolution on the other. Most importantly, it requires bringing together disparate multi-wavelength and multi-resolution spectro-photometric datasets in an homogeneous and well-characterized manner so that they are suitable for a rigorous statistical analysis. The Herschel Extragalactic Legacy Project (HELP) funded by the EC FP7 SPACE program aims to achieve this goal by combining the expertise of optical, infrared and radio astronomers to provide a multi-wavelength database for the distant Universe as an accessible value-added resource for the astronomical community. It will do so by bringing together multi-wavelength datasets covering the 1000 deg$^2$...

  17. Quasar emission lines, radio structures and radio unification

    CERN Document Server

    Jackson, Neal

    2012-01-01

    Unified schemes of radio sources, which account for different types of radio AGN in terms of anisotropic radio and optical emission, together with different orientations of the ejection axis to the line of sight, have been invoked for many years. Recently, large samples of optical quasars, mainly from the Sloan Digital Sky Survey, together with large radio samples, such as FIRST, have become available. These hold the promise of providing more stringent tests of unified schemes but, compared to previous samples, lack high resolution radio maps. Nevertheless they have been used to investigate unified schemes, in some cases yielding results which appear inconsistent with such theories. Here we investigate using simulations how the selection effects to which such investigations are subject can influence the conclusions drawn. In particular, we find that the effects of limited resolution do not allow core-dominated radio sources to be fully represented in the samples, that the effects of limited sensitivity system...

  18. A Radio Astronomy Curriculum for the Middle School Classroom

    Science.gov (United States)

    Davis, J.; Finley, D. G.

    2000-12-01

    In the summer of 2000, two teachers working on a Masters of Science Teaching program at New Mexico Institute of Mining and Technology, spent eight weeks as interns at the Array Operations Center for the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico, under the auspices of the National Science Foundation's (NSF) Research Experience for Teachers (RET) program. The resulting projects will directly benefit students in the indvidual classrooms, as well as provide an easy-to-access resource for other educators. One of the products is a Radio Astronomy Curriculum for upper middle school classes. Radio astronomy images, based on scientific research results using NRAO's Very Large Array, are featured on trading cards which include an explanation, a ``web challenge'', and in some cases, a comparison of radio and optical images. Each trading card has corresponding lesson plans with background information about the images and astronomy concepts needed to do the lessons. Comparison of optical and radio astronomy is used as much as possible to explain the information from research using visible and radio wavelengths. New Mexico's Content Standards and Benchmarks (developed using national standards) for science education was used as a guide for the activities. The three strands of science listed in the standards, Unifying Concepts and Processes, Science as Inquiry, and Science Content are addressed in the lessons. Higher level thinking and problem solving skills are featured throughout the curriculum. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. The NSF's RET program is gratefully acknowledged.

  19. Radio AGN in the local universe: unification, triggering and evolution

    Science.gov (United States)

    Tadhunter, Clive

    2016-06-01

    Associated with one of the most important forms of active galactic nucleus (AGN) feedback, and showing a strong preference for giant elliptical host galaxies, radio AGN (L_{1.4 GHz} > 10^{24} W Hz^{-1}) are a key sub-class of the overall AGN population. Recently their study has benefitted dramatically from the availability of high-quality data covering the X-ray to far-IR wavelength range obtained with the current generation of ground- and space-based telescope facilities. Reflecting this progress, here I review our current state of understanding of the population of radio AGN at low and intermediate redshifts (z < 0.7), concentrating on their nuclear AGN and host galaxy properties, and covering three interlocking themes: the classification of radio AGN and its interpretation; the triggering and fuelling of the jet and AGN activity; and the evolution of the host galaxies. I show that much of the observed diversity in the AGN properties of radio AGN can be explained in terms of a combination of orientation/anisotropy, mass accretion rate, and variability effects. The detailed morphologies of the host galaxies are consistent with the triggering of strong-line radio galaxies (SLRG) in galaxy mergers. However, the star formation properties and cool ISM contents suggest that the triggering mergers are relatively minor in terms of their gas masses in most cases, and would not lead to major growth of the supermassive black holes and stellar bulges; therefore, apart from a minority (<20 %) that show evidence for higher star formation rates and more massive cool ISM reservoirs, the SLRG represent late-time re-triggering of activity in mature giant elliptical galaxies. In contrast, the host and environmental properties of weak-line radio galaxies (WLRG) with Fanaroff-Riley class I radio morphologies are consistent with more gradual fuelling of the activity via gas accretion at low rates onto the supermassive black holes.

  20. The coexistence of cognitive radio and radio astronomy

    OpenAIRE

    Bentum, M. J.; Boonstra, A. J.; Baan, W. A.

    2009-01-01

    An increase of the efficiency of spectrum usage requires the development of new communication techniques. Cognitive radio may be one of those new technique, which uses unoccupied frequency bands for communications. This will lead to more power in the bands and therefore an increasing level of Radio Frequency Interference (RFI), which would cause loss of operation particularly for passive users of the spectrum, such as radio astronomy. This paper will address this issue and will present calcul...

  1. The Rotation Period and Magnetic Field of the T Dwarf 2MASSI J1047539+212423 Measured From Periodic Radio Bursts

    OpenAIRE

    Williams, P. K. G.; Berger, E.

    2015-01-01

    Periodic radio bursts from very low mass stars and brown dwarfs simultaneously probe their magnetic and rotational properties. The brown dwarf 2MASSI J1047539+212423 (2M 1047+21) is currently the only T dwarf (T6.5) detected at radio wavelengths. Previous observations of this source with the Arecibo observatory revealed intermittent, 100%-polarized radio pulses similar to those detected from other brown dwarfs, but were unable to constrain a pulse periodicity; previous VLA observations detect...

  2. Compact radio cores in radio-quiet AGNs

    CERN Document Server

    Maini, Alessandro; Norris, Ray P; Giovannini, Gabriele; Spitler, Lee R

    2016-01-01

    The mechanism of radio emission in radio-quiet (RQ) active galactic nuclei (AGN) is still debated and might arise from the central AGN, from star formation activity in the host, or from either of these sources. A direct detection of compact and bright radio cores embedded in sources that are classified as RQ can unambiguously determine whether a central AGN significantly contributes to the radio emission. We search for compact, high-surface-brightness radio cores in RQ AGNs that are caused unambiguously by AGN activity. We used the Australian Long Baseline Array to search for compact radio cores in four RQ AGNs located in the Extended Chandra Deep Field South (ECDFS). We also targeted four radio-loud (RL) AGNs as a control sample. We detected compact and bright radio cores in two AGNs that are classified as RQ and in one that is classified as RL. Two RL AGNs were not imaged because the quality of the observations was too poor. We report on a first direct evidence of radio cores in RQ AGNs at cosmological reds...

  3. Testing protoplanetary disc dispersal with radio emission

    CERN Document Server

    Owen, James E; Ercolano, Barbara

    2013-01-01

    We consider continuum free-free radio emission from the upper atmosphere of protoplanetary discs as a probe of the ionized luminosity impinging upon the disc. Making use of previously computed hydrodynamic models of disc photoevaporation within the framework of EUV and X-ray irradiation, we use radiative transfer post-processing techniques to predict the expected free-free emission from protoplanetary discs. In general, the free-free luminosity scales roughly linearly with ionizing luminosity in both EUV and X-ray driven scenarios, where the emission dominates over the dust tail of the disc and is partial optically thin at cm wavelengths. We perform a test observation of GM Aur at 14-18 Ghz and detect an excess of radio emission above the dust tail to a very high level of confidence. The observed flux density and spectral index are consistent with free-free emission from the ionized disc in either the EUV or X-ray driven scenario. Finally, we suggest a possible route to testing the EUV and X-ray driven disper...

  4. Wavelength flattened directional couplers for mirrorsymmetric interferometers

    OpenAIRE

    Tormen, Maurizio; Cherchi, Matteo

    2009-01-01

    In the context of guided optics, we derive, analytically and geometrically, a rigorous general criterion to design wavelength insensitive interferometers with mirror symmetry, which are needed for wavelength multiplexing/demultiplexing. The criterion is applied to a practical case, resulting in an interferometer that works on a band wider than 70 nm.

  5. Flexible Adaptation in Cognitive Radios

    CERN Document Server

    Li, Shujun

    2013-01-01

    This book provides an introduction to software-defined radio and cognitive radio, along with methodologies for applying knowledge representation, semantic web, logic reasoning and artificial intelligence to cognitive radio, enabling autonomous adaptation and flexible signaling. Readers from the wireless communications and software-defined radio communities will use this book as a reference to extend software-defined radio to cognitive radio, using the semantic technology described. Readers with a background in semantic web and artificial intelligence will find in this book the application of semantic web and artificial intelligence technologies to wireless communications. For readers in networks and network management, this book presents a new approach to enable interoperability, collaborative optimization and flexible adaptation of network components. Provides a comprehensive ontology covering the core concepts of wireless communications using a formal language; Presents the technical realization of using a ...

  6. Survey Layanan Publik\tPemantauan Frekuensi Radio untuk Radio Amatir Dan Radio Antar Penduduk Indonesia

    Directory of Open Access Journals (Sweden)

    Azwar Aziz

    2014-03-01

    Full Text Available Berlatar belakang fenomena penggunaan amatir radio dan komunikasi radio antar penduduk yang berkaitan dengan faktor layanan publik dari monitor frekuensi radio, dimana peneliti memfokuskan pada permasalahan kondisi pelayanan publik yang diberikan oleh pemerintah tentang penggunaan radio non komersial yang digunakan oleh perorangan. Penelitian ini memperlihatkan penggiat amatir radio dan komunikasi radio antar penduduk bervariasi, mulai dari yang tidak mempunyai izin sampai pada yang memiliki izin. Begitu  juga  peran  tokoh  yang  selalu  mempelopori  tentang berkembangnya potensi amatir radio dan radio antar penduduk ini untuk mengatasi kemashalatan yang ada di Masyarakat. Dengan metode Kualitatif, peneliti melakukan wawancara mendalam untuk mendapatkan kondisi yang sebenarnya dari layanan publik yang telah dilakukan oleh pemerintah maupun oleh pihak organisasi yang membangkitkan potensi untuk menjadi suatu daya yang besar dalam memberikan dukungan komunikasi berkaitan dengan tanggap darurat terkait dengan bencana dan keadaan sosial lainnya. Hasil penelitian menunjukkan bahwa layanan publik diberikan oleh pemerintah di bidang penertiban sangat kurang sehingga frekuensi radio yang digunakan oleh radio perorangan ini tidak kondusif untuk digunakan, hal ini akan mempunyai dampak kemampuan organisasi untuk mengembangkan diri, pengabdian masyarakat dalam mendukung komunikasi tanggap darurat yang setiap saat bisa terjadi.

  7. The properties of radio ellipticals

    International Nuclear Information System (INIS)

    Optical and additional radio data are presented for the bright galaxies of the Disney and Wall survey (1977 Mon. Not. R. Astron. Soc. 179, 235). These data form the basis of a statistical comparison of the properties of radio elliptical galaxies to radio-quiet ellipticals. The correlations may be explained by the depth of the gravitational potential well in which the galaxy resides governing the circumstances under which an elliptical galaxy rids itself of internally produced gas. (author)

  8. Optical spectra of distant radio loud quasars. I. Data: spectra of 67 quasars

    International Nuclear Information System (INIS)

    We present spectra of 67 radio-loud quasars (1.5 em < 3.8) covering the wavelength range 3380 - 7780A at a resolution of about 5 A. Accurate redshifts, emission line strengths, widths and positions are given. A total of 1198 absorption lines were found, including 138 metal line systems, of which 68 show CIV and 60 MgII

  9. The ionization of the emission-line gas in young radio galaxies

    NARCIS (Netherlands)

    Holt, J.; Tadhunter, C. N.; Morganti, R.

    2009-01-01

    This paper is the second in a series in which we present intermediate-resolution, wide-wavelength coverage spectra for a complete sample of 14 compact radio sources, taken with the aim of investigating the impact of the nuclear activity on the circumnuclear interstellar medium (ISM) in the early sta

  10. Radio-induced brain lesions

    Directory of Open Access Journals (Sweden)

    Gorgan Mircea Radu

    2014-03-01

    Full Text Available Introduction : Radiotherapy, an important tool in multimodal oncologic treatment, can cause radio-induced brain lesion development after a long period of time following irradiation.

  11. 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.

  12. Radio Frequency Anechoic Chamber Facility

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Supports the design, manufacture, and test of antenna systems. The facility is also used as an electromagnetic compatibility/radio frequency interference...

  13. The relationship between radio power at 22 and 43 GHz and black hole properties of AGN in elliptical galaxies

    Science.gov (United States)

    Park, Songyoun; Sohn, Bong Won; Yi, Sukyoung K.

    2013-12-01

    We investigate the relationship between radio power and properties related to active galactic nuclei (AGNs). Radio power at 1.4 or 5 GHz, which has been used in many studies, can be affected by synchrotron self-absorption and free-free absorption in a dense region. On the other hand, these absorption effects get smaller at higher frequencies. Thus, we performed simultaneous observations at 22 and 43 GHz using the Korean VLBI Network (KVN) radio telescope based on a sample of 305 AGN candidates residing in elliptical galaxies from the overlap between the Sloan Digital Sky Survey (SDSS) Data Release 7 and Faint Images of the Radio Sky at Twenty-Centimeters (FIRST). About 37% and 22% of the galaxies are detected at 22 and 43 GHz, respectively. Assuming no flux variability between the FIRST and KVN observations, spectral indices were derived from FIRST and KVN data and we found that over 70% of the detected galaxies have flat or inverted spectra, implying the presence of optically thick compact regions near the centres of the galaxies. Core radio power does not show a clear dependence on black hole mass at either low (1.4 GHz) or high (22 and 43 GHz) frequencies. However, we found that the luminosity of the [OIII] λ5007 emission line and the Eddington ratio correlate with radio power more closely at high frequencies than at low frequencies. This suggests that radio observation at high frequencies can be an appropriate tool for unveiling the innermost region. In addition, the luminosity of the [OIII] λ5007 emission line and the Eddington ratio can be used as a tracer of AGN activity. Our study suggests a causal connection between high frequency radio power and optical properties of AGNs. Table 5 is available in electronic form at http://www.aanda.org

  14. RADIO FREQUENCY ATTENUATOR

    Science.gov (United States)

    Giordano, S.

    1963-11-12

    A high peak power level r-f attenuator that is readily and easily insertable along a coaxial cable having an inner conductor and an outer annular conductor without breaking the ends thereof is presented. Spaced first and second flares in the outer conductor face each other with a slidable cylindrical outer conductor portion therebetween. Dielectric means, such as water, contact the cable between the flares to attenuate the radio-frequency energy received thereby. The cylindrical outer conductor portion is slidable to adjust the voltage standing wave ratio to a low level, and one of the flares is slidable to adjust the attenuation level. An integral dielectric container is also provided. (AFC)

  15. Radio-Communications Architectures

    OpenAIRE

    Diet, Antoine; Villegas, Martine; Baudoin, Genevieve; Robert, Fabien

    2010-01-01

    The goal of this chapter is to demonstrate the absolute need of matching the architecture design and the signal carrying the information. In section 1 and 2, considerations about current users' needs helped to identify three types of carrier signals in the context of radio-communications: NB-CW, WB-CW and IR. A separation between CW and IR signals is unavoidable because it drives us to a different technological design. Basic blocks of transmitter architecture are optimized in function with th...

  16. Educational Radio: A Review of the Literature.

    Science.gov (United States)

    Grise, Philip J., Jr.; And Others

    Radio has been used for educational purposes since its beginning in the early 1920's; the application of radio to the educational problems of the developing nations is not a new concept by any means. Among the uses of educational radio are foreign radio schools, classroom radio uses, "Accion Cultural Popular" (ACPO), and correspondence radio…

  17. How else can we detect Fast Radio Bursts?

    CERN Document Server

    Lyutikov, Maxim

    2016-01-01

    We discuss possible electromagnetic signals accompanying Fast Radio Bursts (FRBs) that are expected in the scenario where FRBs originate in neutron star magnetospheres. For models involving Crab-like giant pulses, no appreciable contemporaneous emission is expected at other wavelengths. Magnetar giant flares, driven by the reconfiguration of the magnetosphere, however, can produce both contemporaneous bursts at other wavelengths as well as afterglow-like emission. We conclude that the best chances are: (i) prompt short GRB-like emission; (ii) a contemporaneous optical flash that can reach naked eye peak luminosity (but only for a few milliseconds); (iii) a high energy afterglow emission. Case (i) could be tested by coordinated radio and high-energy experiments. Case (ii) could be seen by the Palomar Transient Factory in a 60-second frame as a transient object of $m=15-20$ magnitude with an expected optical detection rate of about 0.1~hr$^{-1}$, an order of magnitude higher than in radio. EVRYSCOPE could also ...

  18. The coexistence of cognitive radio and radio astronomy

    NARCIS (Netherlands)

    Bentum, M.J.; Boonstra, A.J.; Baan, W.A.

    2009-01-01

    An increase of the efficiency of spectrum usage requires the development of new communication techniques. Cognitive radio may be one of those new technique, which uses unoccupied frequency bands for communications. This will lead to more power in the bands and therefore an increasing level of Radio

  19. ETSI reconfigurable radio systems : Status and future directions on software defined radio and cognitive radio standards

    OpenAIRE

    Mueck M.; Piipponen A.; Kalliojarvi K.; Dimitrakopoulos G.; Tsagkaris K.; Demestichas P.; Casadevall F.; Perez-Romero J.; Sallent O.; Baldini G.

    2010-01-01

    Feature Topic on Advances in IEEE Standards and Testbeds for Cognitive Radio Networks International audience This article details the current work status of the ETSI Reconfigurable Radio Systems Techni- cal Committee, positions the ETSI work with respect to other standards efforts (IEEE 802, IEEE SCC41) as well as the European Regula- tory Framework, and gives an outlook on the future evolution. In particular, software defined radio related study results are presented with a focus on SD...

  20. High resolution radio observations of nuclear and circumnuclear regions of luminous infrared galaxies (LIRGs)

    International Nuclear Information System (INIS)

    High-resolution radio observations of the nuclear region of Luminous and Ultraluminous Infrared Galaxies (ULIRGs) have shown that its radio structure consists of a compact high surface-brightness central radio source immersed in a diffuse low brightness circumnuclear halo. While the central component could be associated with an AGN or compact star-forming regions where radio supernovae are exploding, it is well known that the circumnuclear regions host bursts of star-formation. The studies of radio supernovae can provide essential information about stellar evolution and CSM/ISM properties in regions hidden by dust at optical and IR wavelengths. In this contribution, we show results from radio interferometric observations from NGC 7469, IRAS 18293-3413 and IRAS 17138-1017 where three extremely bright radio supernovae have been found. High-resolution radio observations of these and other LIRGs would allow us to determine the core-collapse supernova rate in them as well as their star-formation rate.

  1. Are Homologous Radio Bursts Driven by Solar Post-Flare Loops?

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Three particularly complex radio bursts (2001 October 19, 2001 April 10 and 2003 October 26) obtained with the spectrometers (0.65-7.6 GHz) at the National Astronomical Observatories, Chinese Academy of Sciences (NAOC, Beijing and Yunnan) and other instruments (NoRH, TRACE and SXT) are presented. They each have two groups of peaks occurring in different frequency ranges (broad-band microwave and narrow-band decimeter wavelengths). We stress that the second group of burst peaks that occurred in the late phase of the flares and associated with post-flare loops may be homologous radio bursts. We think that they are driven by the post-flare loops. In contrast to the time profiles of the radio bursts and the images of coronal magnetic polarities, we are able to find that the three events are caused by the active regions including main single-bipole magnetic structures, which are associated with multipole magnetic structures during the flare evolutions. In particular, we point out that the later decimetric radio bursts are possibly the radio counterparts of the homologous flares (called "homologous radio bursts" by us), which are also driven by the single-bipole magnetic structures. By examining the evolutions of the magnetic polarities of sources (17 GHz),we could presume that the drivers of the homologous radio bursts are new and/or recurring appearances/disappearances of the magnetic polarities of radio sources, and that the triggers are the magnetic reconnections of single-bipole configurations.

  2. Reflectivity and Braggs Wavelength in FBG

    Directory of Open Access Journals (Sweden)

    Dinesh Arora

    2011-12-01

    Full Text Available We have presented an analytical model of splitters based on Fiber Bragg grating used to detect a Bragg wavelength from the number of wavelengths which are traveling in an optical fiber. The number of grids and grating length can be used as a wavelength shifter.This paper presents experimental results that are used to show the effect of number of grids and the length of the grating on the Bragg wavelength and reflectivity of Fiber Bragg Grating (FBG. The pitch of grating is directly proportional to the grating length and inversely proportional to number of grids. When the grating length is fixed and the number of grids is increased, the Bragg wavelength decreases and reflectivity increases. This increase in reflectivity is very small. Further when the number of grids was kept constant and the grating length was increased the Bragg wavelength increases. The effect of this increase in grating length on reflectivity is a very small. In our model, the effectiveness of the grating in extracting the Braggs wavelength is nearly 100%.

  3. Origin and nature of Radio-Loud Broad Absorption Line Quasars. A multi-wavelength study

    OpenAIRE

    Bruni, Gabriele

    2012-01-01

    RESUMEN: El origen de los cuásares con líneas anchas de absorción (BAL QSOs, del acrónimo en inglés Broad Absorption Line Quasars) es un tema todavía en discusión. Representando aproximadamente un 20% de la población de QSOs, estos objetos muestran líneas de absorción muy anchas en su espectro óptico/UV que están generadas por flujos de material que emerge con velocidades de hasta 0.2c. No existe consenso sobre el origen de este gas causante de las absorciones, ni del mecanismo que lo acelera...

  4. Astronomical polarization studies at radio and infrared wavelengths. Part 1: Gravitational deflection of polarized radiation

    Science.gov (United States)

    Dennison, B. K.

    1976-01-01

    The gravitational field is probed in a search for polarization dependence in the light bending. This involves searching for a splitting of a source image into orthogonal polarizations as the radiation passes through the solar gravitational field. This search was carried out using the techniques of very long and intermediate baseline interferometry, and by seeking a relative phase delay in orthogonal polarizations of microwaves passing through the solar gravitational field. In this last technique a change in the total polarization of the Helios 1 carrier wave was sought as the spacecraft passed behind the sun. No polarization splitting was detected.

  5. Radio over fiber broadband access networks architectures based on wavelength division multiplexing techniques

    OpenAIRE

    Avó, Ricardo Pedro Custodinho da

    2013-01-01

    The recent remarkable growth in bandwidth of both wired optical and wireless access networks supports a burst of new high bandwidth Internet applications such as: peer-topeer file sharing, cloud storage, on-line gaming, video streaming, etc. Within this scenario, the convergence of fixed and wireless access networks offers significant opportunities for network operators to satisfy user demands, and simultaneously reduce the cost of implementing and running separated wireless an...

  6. Infrared-Faint Radio Sources in the SERVS deep fields: Pinpointing AGNs at high redshift

    CERN Document Server

    Maini, Alessandro; Norris, Ray P; Spitler, Lee R; Mignano, Arturo; Lacy, Mark; Morganti, Raffaella

    2016-01-01

    Infrared-Faint Radio Sources (IFRS) represent an unexpected class of objects relatively bright at radio wavelength, but unusually faint at infrared (IR) and optical wavelengths. A recent and extensive campaign on the radio-brightest IFRSs (S_{1.4GHz} >= 10 mJy) has provided evidence that most of them (if not all) contain an AGN. Still uncertain is the nature of the radio-faintest ones (S_{1.4GHz} 4). We analysed a number of IFRS samples identified in SERVS fields, including a new sample (21 sources) extracted from the Lockman Hole. 3.6 and 4.5 mum IR counterparts of the 64 sources located in the SERVS fields were searched for, and, when detected, their IR properties were studied. We compared the radio/IR properties of the IR-detected IFRSs with those expected for a number of known classes of objects. We found that they are mostly consistent with a mixture of high-redshift (z >= 3) radio-loud AGNs. The faintest ones (S_{1.4GHz} ~ 100 muJy), however, could be also associated with nearer (z ~ 2) dust-enshrouded...

  7. Synoptic solar radio observations as proxies for upper atmosphere modelling

    CERN Document Server

    de Wit, Thierry Dudok; Shibasaki, Kiyoto

    2014-01-01

    The specification of the upper atmosphere strongly relies on solar proxies that can properly reproduce the solar energetic input in the UV. Whilst the microwave flux at 10.7 cm (also called F10.7 index) has been routinely used as a solar proxy, we show that the radio flux at other wavelengths provides valuable complementary information that enhances their value for upper atmospheric modelling. We merged daily observations from various observatories into a single homogeneous data set of fluxes at wavelengths of 30, 15, 10.7, 8 and 3.2 cm, spanning from 1957 to today. Using blind source separation (BSS), we show that their rotational modulation contains three contributions, which can be interpreted in terms of thermal bremsstrahlung and gyro-resonance emissions. The latter account for 90% of the rotational variability in the F10.7 index. Most solar proxies, such as the MgII index, are remarkably well reconstructed by simple linear combination of radio fluxes at various wavelengths. The flux at 30 cm stands out ...

  8. Silicon photonic waveguides for different wavelength regions

    International Nuclear Information System (INIS)

    In this paper, we present our work on three silicon waveguide structures that are suitable for three different wavelength regions: near-, mid- and far-infrared. Design rules for standard rib SOI waveguides are given. Both single mode and polarization independence in these waveguides are discussed. A hollow-core waveguide suitable for gas-sensing applications in the mid-infrared wavelength region is also analysed. Finally, fabrication and experimental results for free standing waveguides, which may find application in the mid- and perhaps far-infrared wavelength regions, are presented

  9. Wavelength Shifting Efficiency of Tetraphenyl Butadiene (TPB) at Extreme Ultraviolet Wavelengths

    Science.gov (United States)

    Benson, Christopher; Orebi Gann, Gabriel; Gehman, Victor

    2015-10-01

    Tetraphenyl Butadiene (TPB) is a commonly used wavelength shifter (WLS) in neutrino and dark matter liquid noble gas scintillator detectors. Thin films of wavelength shifters are used to shift ultraviolet scintillation light into the visible spectrum for event reconstruction. The wavelength shifting efficiency of TPB is a function of the incident ultraviolet photon wavelength and is an important parameter for detector design, simulation and reconstruction. The wavelength shifting efficiency and emission spectrum has been previously measured down to 120 nm [Gehman et al., 2011]. To build liquid noble gas scintillator detectors with lighter elements (Ne, He) that use TPB as a WLS medium, the wavelength shifting efficiency must be known closer to 80 nm. This talk will present the current status and preliminary results from a set of measurements that will improve the precision of the efficiency of 120 nm, and extend the data to wavelengths as low as 45 nm.

  10. JUICE/RPWI/JENRAGE: a low frequency radio imager at Jupiter

    Science.gov (United States)

    Cecconi, B.; Kasaba, Y.; Bergman, J. E. S.; Zarka, P.; Lamy, L.; Hess, S. L. G.; Rothkaehl, H.

    2015-10-01

    The JENRAGE (Jovian Environment Radio Astronomy and Ganymede Exploration) experiment of the Radio and Plasma Waves Instrument (RPWI) on-board JUICE (Jupiter Icy Moon Explorer) is a sensitive, and versatile radio instrument. It will observe radio waves ranging from 80 kHz to 45 MHz at a 100 Msample per second aquisition rate. The instrument is composed of set of 3 electrical dipoles (developed by the Polish team), connected to low noise preamplifiers and conditioning analog filters (built by the Japanese team), then sampled and digitally filtererd into ~300 kHz bands (digital part developed by the Swedish team). This international project is coordinated by B. Cecconi and Y. Kasaba, both co-PI of JUICE/RPWI. Although the radio antenna connected to this instrument have no intrinsic directivity, the JENRAGE measurements can provide instantaneous direction of arrival, flux density and polarization degree of the observed radio waves. Hence, the JENRAGE can be described as an full-sky radio imager. As the instrument provides direction of arrival, radio sources can be located with some assumption on the propagation between the source and the observer. Hence, it is possible to produce radio source maps and correlate them with observations at other wavelengths, such as UV or IR observations of the auroral regions of Jupiter. The flux and polarization measurements together with the time- frequency shape of the radio emissions can also be used to identify the radio emission processes. These features have shown their capabilities on Cassini, with the RPWS/HFR instrument. We will present the JUICE/RPWI/JENRAGE design and the science objectives. Additional science topics linked to the icy satellites, which are currently being assessed, will also be presented.

  11. Radio and spectroscopic properties of miniature radio galaxies: revealing the bulk of the radio-loud AGN population

    OpenAIRE

    Baldi, Ranieri D.; Capetti, Alessandro

    2009-01-01

    We explore radio and spectroscopic properties of a sample of 14 miniature radio galaxies, i.e. early-type core galaxies hosting radio-loud AGN of extremely low radio power, 10^(27-29) erg s^(-1) Hz^(-1) at 1.4 GHz. Miniature radio galaxies smoothly extend the relationships found for the more powerful FRI radio galaxies between emission line, optical and radio nuclear luminosities to lower levels. However, they have a deficit of a factor of ~100 in extended radio emission with respect to that ...

  12. Radio Relics in Cosmological Simulations

    Indian Academy of Sciences (India)

    M. Hoeft; S. E. Nuza; S. Gottlöber; R. J. van Weeren; H. J. A. Röttgering; M. Brüggen

    2011-12-01

    Radio relics have been discovered in many galaxy clusters. They are believed to trace shock fronts induced by cluster mergers. Cosmological simulations allow us to study merger shocks in detail since the intra-cluster medium is heated by shock dissipation. Using high resolution cosmological simulations, identifying shock fronts and applying a parametric model for the radio emission allows us to simulate the formation of radio relics. We analyze a simulated shock front in detail. We find a rather broad Mach number distribution. The Mach number affects strongly the number density of relativistic electrons in the downstream area, hence, the radio luminosity varies significantly across the shock surface. The abundance of radio relics can be modeled with the help of the radio power probability distribution which aims at predicting radio relic number counts. Since the actual electron acceleration efficiency is not known, predictions for the number counts need to be normalized by the observed number of radio relics. For the characteristics of upcoming low frequency surveys we find that about thousand relics are awaiting discovery.

  13. Tuning in to pavement radio

    NARCIS (Netherlands)

    Ellis, S.D.K.

    1989-01-01

    This article describes a phenomenon known all over Africa, for which there is no really satisfactory term in English but which is summed up in the French term 'radio trottoir', literally 'pavement radio'. It may be defined as the popular and unofficial discussion of current affairs in Africa, partic

  14. Radio Loud AGNs are Mergers

    CERN Document Server

    Chiaberge, Marco; Lotz, Jennifer; Norman, Colin

    2015-01-01

    We measure the merger fraction of Type 2 radio-loud and radio-quiet active galactic nuclei at z>1 using new samples. The objects have HST images taken with WFC3 in the IR channel. These samples are compared to the 3CR sample of radio galaxies at z>1 and to a sample of non-active galaxies. We also consider lower redshift radio galaxies with HST observations and previous generation instruments (NICMOS and WFPC2). The full sample spans an unprecedented range in both redshift and AGN luminosity. We perform statistical tests to determine whether the different samples are differently associated with mergers. We find that all (92%) radio-loud galaxies at z>1 are associated with recent or ongoing merger events. Among the radio-loud population there is no evidence for any dependence of the merger fraction on either redshift or AGN power. For the matched radio-quiet samples, only 38% are merging systems. The merger fraction for the sample of non-active galaxies at z>1 is indistinguishable from radio-quiet objects. This...

  15. The Massive Hosts of Radio Galaxies Across Cosmic Time

    Science.gov (United States)

    Seymour, Nick; SHzRG Collaboration

    2007-05-01

    We present the results of a comprehensive Spitzer survey of 69 radio galaxies across 160% for 75% the high redshift radio galaxies. As expected from unified models of AGN, the stellar fraction of the rest-frame H-band luminosity has no correlation with redshift, radio luminosity, or rest-frame mid-IR (5um) luminosity. Additionally, while the stellar H-band luminosity does not vary with stellar fraction, the total H-band luminosity anti-correlates with the stellar fraction as would be expected if the underlying hosts of these radio galaxies comprise a homogeneous population. The resultant stellar luminosities imply stellar masses of 10^{11-11.5}Msun even at the highest redshifts. Powerful radio galaxies tend to lie in a similar region of mid-IR color-color space as unobscured AGN, despite the stellar contribution to their mid-IR SEDs at shorter-wavelengths. The mid-IR luminosities alone classify most HzRGs as LIRGs or ULIRGs with even higher total-IR luminosities. As expected, these exceptionally high mid-IR luminosities are consistent with an obscured, highly-accreting AGN. Sub-mm observed starformation rates imply very high specific starformation rates, higher than other massive galaxies at these redshift ranges, suggesting we are watching the final formation of massive galaxies and black holes. We also present new evidence that the blackhole accretion rate (from mid-IR luminosity) correlates with radio lobe size and anti-correlates with specific starformation rate, begging the question which came first?

  16. Modeling UHF Radio Propagation in Buildings.

    Science.gov (United States)

    Honcharenko, Walter

    The potential implementation of wireless Radio Local Area Networks and Personal Communication Services inside buildings requires a thorough understanding of signal propagation within buildings. This work describes a study leading to a theoretical understanding of wave propagation phenomenon inside buildings. Covered first is propagation in the clear space between the floor and ceiling, which is modeled using Kirchoff -Huygens diffraction theory. This along with ray tracing techniques are used to develop a model to predict signal coverage inside buildings. Simulations were conducted on a hotel building, two office buildings, and a university building to which measurements of CW signals were compared, with good agreement. Propagation to other floors was studied to determine the signal strength as a function of the number of floors separating transmitter and receiver. Diffraction paths and through the floor paths which carry significant power to the receivers were examined. Comparisons were made to measurements in a hotel building and an office building, in which agreements were excellent. As originally developed for Cellular Mobile Radio (CMR) systems, the sector average is obtained from the spatial average of the received signal as the mobile traverses a path of 20 or so wavelengths. This approach has also been applied indoors with the assumption that a unique average could be obtained by moving either end of the radio link. However, unlike in the CMR environment, inside buildings both ends of the radio link are in a rich multipath environment. It is shown both theoretically and experimentally that moving both ends of the link is required to achieve a unique average. Accurate modeling of the short pulse response of a signal within a building will provide insight for determining the hardware necessary for high speed data transmission and recovery, and a model for determining the impulse response is developed in detail. Lastly, the propagation characteristics of

  17. Growth of centimeter-scale atomically thin MoS{sub 2} films by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Siegel, Gene; Venkata Subbaiah, Y. P.; Prestgard, Megan C.; Tiwari, Ashutosh, E-mail: tiwari@eng.utah.edu [Nanostructured Materials Research Laboratory, Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112 (United States)

    2015-05-01

    We are reporting the growth of single layer and few-layer MoS{sub 2} films on single crystal sapphire substrates using a pulsed-laser deposition technique. A pulsed KrF excimer laser (wavelength: 248 nm; pulse width: 25 ns) was used to ablate a polycrystalline MoS{sub 2} target. The material thus ablated was deposited on a single crystal sapphire (0001) substrate kept at 700 °C in an ambient vacuum of 10{sup −6} Torr. Detailed characterization of the films was performed using atomic force microscopy (AFM), Raman spectroscopy, UV-Vis spectroscopy, and photoluminescence (PL) measurements. The ablation of the MoS{sub 2} target by 50 laser pulses (energy density: 1.5 J/cm{sup 2}) was found to result in the formation of a monolayer of MoS{sub 2} as shown by AFM results. In the Raman spectrum, A{sub 1g} and E{sup 1}{sub 2g} peaks were observed at 404.6 cm{sup −1} and 384.5 cm{sup −1} with a spacing of 20.1 cm{sup −1}, confirming the monolayer thickness of the film. The UV-Vis absorption spectrum exhibited two exciton absorption bands at 672 nm (1.85 eV) and 615 nm (2.02 eV), with an energy split of 0.17 eV, which is in excellent agreement with the theoretically predicted value of 0.15 eV. The monolayer MoS{sub 2} exhibited a PL peak at 1.85 eV confirming the direct nature of the band-gap. By varying the number of laser pulses, bi-layer, tri-layer, and few-layer MoS{sub 2} films were prepared. It was found that as the number of monolayers (n) in the MoS{sub 2} films increases, the spacing between the A{sub 1g} and E{sup 1}{sub 2g} Raman peaks (Δf) increases following an empirical relation, Δf=26.45−(15.42)/(1+1.44 n{sup 0.9}) cm{sup −1}.

  18. Radio Emission from Globular Clusters

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Radio emission of globular clusters is studied by analyzing the VLA radio survey data of the NVSS and FIRST. We find that 13 clusters have radio sources within their half-mass radii of clusters. Sources detected previously in NGC 7078and NGC 6440 are identified. Pulsars in NGC 6121, NGC 6440 and NGC 7078cannot be detected because of the insufficient survey sensitivity and resolution.There may be a pulsar in the core of Terzan 1. The nature of the extended radio source near the core of NGC 6440 remains unclear. In the core of a globular cluster,there may be many neutron stars or an intermediate mass black hole, but this cannot be clarified with the current radio observations.

  19. Radio propagation measurement and channel modelling

    CERN Document Server

    Salous, Sana

    2013-01-01

    While there are numerous books describing modern wireless communication systems that contain overviews of radio propagation and radio channel modelling, there are none that contain detailed information on the design, implementation and calibration of radio channel measurement equipment, the planning of experiments and the in depth analysis of measured data. The book would begin with an explanation of the fundamentals of radio wave propagation and progress through a series of topics, including the measurement of radio channel characteristics, radio channel sounders, measurement strategies

  20. Wavelength mismatch effect in electromagnetically induced absorption

    Science.gov (United States)

    Bharti, Vineet; Wasan, Ajay; Natarajan, Vasant

    2016-07-01

    We present a theoretical investigation of the phenomenon of electromagnetically induced absorption (EIA) in a 4-level system consisting of vee and ladder subsystems. The four levels are coupled using one weak probe field, and two strong control fields. We consider an experimental realization using energy levels of Rb. This necessitates dealing with different conditions of wavelength mismatch-near-perfect match where all three wavelengths are approximately equal; partial mismatch where the wavelength of one control field is less than the other fields; and complete mismatch where all three wavelengths are unequal. We present probe absorption profiles with Doppler averaging at room temperature to account for experiments in a room temperature Rb vapor cell. Our analysis shows that EIA resonances can be studied using Rydberg states excited with diode lasers.

  1. Wavelength Shifters for Water Cherenkov Detectors

    CERN Document Server

    Dai, Xiongxin; Bellerive, Alain; Hargrove, Cliff; Sinclair, David; Mifflin, Cathy; Zhang Feng

    2008-01-01

    The light yield of a water-based Cherenkov detector can be significantly improved by adding a wavelength shifter. Wavelength shifter (WLS) molecules absorb ultraviolet photons and re-emit them at longer wavelengths where typical photomultiplier tubes are more sensitive. In this study, several wavelength shifter compounds are tested for possible deployment in the Sudbury Neutrino Observatory (SNO). Test results on optical properties and chemical compatibility for a few WLS candidates are reported; together with timing and gain measurements. A Monte Carlo simulation of the SNO detector response is used to estimate the total light gain with WLS. Finally, a cosmic ray Cherenkov detector was built to investigate the optical properties of WLS.

  2. Wavelength dependence of transient photovoltage polarity

    International Nuclear Information System (INIS)

    Using pulsed laser with different wavelengths, transient photovoltage (TPV) is investigated for the sandwich device of indium tin oxide (ITO)/poly (2-methoxy-5-(2'-ethylhexyloxy)-1, 4-phenylenevinylene) (MEH-PPV) (500 nm)/Al. At laser wavelength of 500 nm, a 0.1 millisecond negative TPV signal appears followed by a positive one lasting 40-80 milliseconds. With increasing laser wavelength, the negative signal becomes weak and disappears when wavelengths λ≥560 nm. This work demonstrates the process of exciton dissociation at the interface between ITO and MEH-PPV. A new method measuring the relative dissociation rate at the interface between polymer and electrode is introduced. It is estimated that the dissociation rate at Al interface is 4-8 times of that at the ITO interface

  3. Wavelength mismatch effect in electromagnetically induced absorption

    CERN Document Server

    Bharti, Vineet; Natarajan, Vasant

    2016-01-01

    We present a theoretical investigation of the phenomenon of electromagnetically induced absorption (EIA) in a 4-level system consisting of vee and ladder subsystems. The four levels are coupled using one weak probe field, and two strong control fields. We consider an experimental realization using energy levels of Rb. This necessitates dealing with different conditions of wavelength mismatch---near-perfect match where all three wavelengths are approximately equal; partial mismatch where the wavelength of one control field is less than the other fields; and complete mismatch where all three wavelengths are unequal. We present probe absorption profiles with Doppler averaging at room temperature to account for experiments in a room temperature Rb vapor cell. Our analysis shows that EIA resonances can be studied using Rydberg states excited with diode lasers.

  4. High efficiency dielectric metasurfaces at visible wavelengths

    CERN Document Server

    Devlin, Robert C; Chen, Wei-Ting; Oh, Jaewon; Capasso, Federico

    2016-01-01

    Metasurfaces are planar optical elements that hold promise for overcoming the limitations of refractive and conventional diffractive optics1-3. Dielectric metasurfaces demonstrated thus far4-10 are limited to transparency windows at infrared wavelengths because of significant optical absorption and loss at visible wavelengths. It is critical that new materials and fabrication techniques be developed for dielectric metasurfaces at visible wavelengths to enable applications such as three-dimensional displays, wearable optics and planar optical systems11. Here, we demonstrate high performance titanium dioxide dielectric metasurfaces in the form of holograms for red, green and blue wavelengths with record absolute efficiency (>78%). We use atomic layer deposition of amorphous titanium dioxide that exhibits low surface roughness of 0.738 nm and ideal optical properties. To fabricate the metasurfaces we use a lift-off-like process that allows us to produce highly anisotropic nanofins with shape birefringence. This ...

  5. Wavelength-Dependent Effects in Maxwell Optics

    CERN Document Server

    Khan, S A

    2002-01-01

    We present a new formalism for light beam optics starting with an exact eight-dimensional matrix representation of the Maxwell equations. The Foldy-Wouthuysen iterative diagonalization technique is employed to obtain a Hamiltonian description for a system with varying refractive index. Besides, reproducing all the traditional quasiparaxial terms, this method leads to additional contributions, which are dependent on the wavelength, in the optical Hamiltonian. This alternate prescription to obtain the aberration expansion is applied to the axially symmetric graded index fiber. This results in the wavelength-dependent modifications of the paraxial behaviour and the aberration coefficients. Furthermore it predicts a wavelength-dependent image rotation. In the low wavelength limit our formalism reproduces the Lie algebraic formalism of optics. The Foldy-Wouthuysen technique employed by us is ideally suited for the Lie algebraic approach to optics. The present study further strengthens the close analogy between the...

  6. Wavelength dependence of transient photovoltage polarity

    Energy Technology Data Exchange (ETDEWEB)

    Shi Quanmin [Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China); Hou Yanbing [Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China)], E-mail: ybhou@bjtu.edu.cn; Li Yunbai; Feng Zhihui; Liu Xiaojun [Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China)

    2008-09-01

    Using pulsed laser with different wavelengths, transient photovoltage (TPV) is investigated for the sandwich device of indium tin oxide (ITO)/poly (2-methoxy-5-(2'-ethylhexyloxy)-1, 4-phenylenevinylene) (MEH-PPV) (500 nm)/Al. At laser wavelength of 500 nm, a 0.1 millisecond negative TPV signal appears followed by a positive one lasting 40-80 milliseconds. With increasing laser wavelength, the negative signal becomes weak and disappears when wavelengths {lambda}{>=}560 nm. This work demonstrates the process of exciton dissociation at the interface between ITO and MEH-PPV. A new method measuring the relative dissociation rate at the interface between polymer and electrode is introduced. It is estimated that the dissociation rate at Al interface is 4-8 times of that at the ITO interface.

  7. Multi-Wavelength Variability Properties of Fermi Blazar S5 0716+714

    Indian Academy of Sciences (India)

    N. H. Liao; J. M. Bai; H. T. Liu; S. S. Weng; Liang Chen; F. Li

    2014-09-01

    The multi-wavelength variability properties of blazar S5 0716 + 714 are reported. We construct multi-wavelength light curves of radio, optical, X-ray and -ray including our optical observation at Yunnan Observatories. In all the bands, the light curves show intense variabilities. The variability amplitudes in -ray and optical bands are larger than those in the hard X-ray and radio bands. The characteristic variability timescales at 14.5 GHz, optical, X-ray, and -ray bands are comparable. The variations of the hard X-ray and 14.5GHz emissions are correlated with zero lag, and so are the V band and -ray variations. The multi-wavelength variability behaviours can be naturally explained by the classic leptonic model. We model the average SED of S5 0716 + 714 by leptonic model. The SSC+ERC model using the external seed photons from hot dust or Broad Line Region (BLR) emission is probably favourable avoiding the extreme input parameters from the pure SSC model.

  8. On the connection between radio and gamma rays

    Directory of Open Access Journals (Sweden)

    Orienti M.

    2013-12-01

    Full Text Available Relativistic jets are one of the most powerful manifestations of the release of energy produced around supermassive black holes at the centre of active galactic nuclei (AGN. Their emission is observed across the entire electromagnetic spectrum, from the radio band to gamma rays. Despite decades of efforts, many aspects of the physics of relativistic jets remain elusive. In particular, the location and the mechanisms responsible for the high-energy emission and the connection of the variability at different wavelengths are among the greatest challenges in the study of AGN. From the comparison of the radio and gamma-ray light curves of gamma-ray flaring objects, there is evidence that some flares, either in radio or in gamma rays, have not an obvious connection at the other extreme of the electromagnetic spectrum, like in the case of the Narrow-Line Seyfert 1 SBS 0846+513. An intriguing aspect pointed out by high resolution radio observations is the change of the polarization properties close in time with some high energy flares. In particular, in PKS 1510–089 and 3C 454.3 a rotation of almost 90 degrees has been observed after strong gamma-ray flares. The swing of the polarization angle may be related either to the propagation of a shock along the jet that orders the magnetic field, or a change of the opacity regime.

  9. A Radio Transient 0.1 pc from Sagittarius A*

    CERN Document Server

    Bower, G C; Yusef-Zadeh, F; Backer, D C; Cotton, W D; Goss, W M; Lang, C C; Lithwick, Y; Bower, Geoffrey C.; Roberts, Doug A.; Yusef-Zadeh, Farhad; Backer, Donald C.; Lang, Cornelia C.; Lithwick, Yoram

    2005-01-01

    We report the discovery of a transient radio source 2.7 arcsec (0.1 pc projected distance) South of the Galactic Center massive black hole, Sagittarius A*. The source flared with a peak of at least 80 mJy in March 2004. The source was resolved by the Very Large Array into two components with a separation of ~0.7 arcsec and characteristic sizes of ~0.2 arcsec. The two components of the source faded with a power-law index of 1.1 +/- 0.1. We detect an upper limit to the proper motion of the Eastern component of ~3 x 10^3 km s^-1 relative to Sgr A*. We detect a proper motion of ~10^4 km s^-1 for the Western component relative to Sgr A*. The transient was also detected at X-ray wavelengths with the Chandra X-ray Observatory and the XMM-Newton telescope and given the designation CXOGC J174540.0-290031. The X-ray source falls in between the two radio components. The maximum luminosity of the X-ray source is ~10^36 erg s^-1, significantly sub-Eddington. The radio jet flux density predicted by the X-ray/radio correlat...

  10. Large-scale radio structure of R Aquarii

    Energy Technology Data Exchange (ETDEWEB)

    Hollis, J.M.; Michalitsianos, A.G.; Oliversen, R.J.; Yusef-Zadeh, F.; Kafatos, M.

    1987-10-01

    Radio continuum observations of the R Aqr symbiotic star system, using the compact D configuration of the VLA at 6-cm wavelength, reveal a large-scale about 2-arcmin structure engulfing the binary, which has long been known to have a similar optical nebula. This optical/radio nebula possesses about 4 x 10 to the 42nd ergs of kinetic energy which is typical of a recurrent nova outburst. Moreover, a cluster of a dozen additional 6-cm radio sources were observed in proximity to R Aqr, most of these discrete sources lie about 3 arcmin south and/or west of R Aqr and, coupled with previous 20-cm data, spectral indices limits suggest a thermal nature for some of these sources. If the thermal members of the cluster are associated with R Aqr, it may indicate a prehistoric eruption of the system's suspected recurrent nova. The nonthermal cluster members may be extragalactic background radio sources. 15 references.

  11. The far-infrared/radio correlation as probed by Herschel

    CERN Document Server

    Ivison, R J; Ibar, E; Andreani, P; Elbaz, D; Altieri, B; Amblard, A; Arumugam, V; Auld, R; Aussel, H; Babbedge, T; Berta, S; Blain, A; Bock, J; Bongiovanni, A; Boselli, A; Buat, V; Burgarella, D; Castro, N; Cava, A; Cepa, J; Chanial, P; Cimatti, A; Cirasuolo, M; Clements, D L; Conley, A; Conversi, L; Cooray, A; Daddi, E; Dominguez, H; Dowell, C D; Dwek, E; Eales, S; Farrah, D; Fox, M; Franceschini, A; Gear, W; Genzel, R; Glenn, J; Griffin, M; Gruppioni, C; Halpern, M; Hatziminaoglou, E; Isaak, K; Lagache, G; Levenson, L; Lu, N; Lutz, D; Madden, S; Maffei, B; Magdis, G; Mainetti, G; Maiolino, R; Marchetti, L; Morrison, G E; Mortier, A M J; Nguyen, H T; Nordon, R; O'Halloran, B; Oliver, S J; Omont, A; Owen, F N; Page, M J; Panuzzo, P; Papageorgiou, A; Pearson, C P; A.,; Poglitsch, A; Pohlen, M; Popesso, P; Pozzi, F; Rawlings, J I; Raymond, G; Rigopoulou, D; Riguccini, L; Rizzo, D; Rodighiero, G; Roseboom, I G; Rowan-Robinson, M; Saintonge, A; Portal, M Sanchez; Santini, P; Schulz, B; Scott, Douglas; Seymour, N; Shao, L; Shupe, D L; Smith, A J; Stevens, J A; Sturm, E; Symeonidis, M; Tacconi, L; Trichas, M; Tugwell, K E; Vaccari, M; Valtchanov, I; Vieira, J; Vigroux, L; Wang, L; Ward, R; Wright, G; Xu, C K; Zemcov, M

    2010-01-01

    We set out to determine the ratio, q(IR), of rest-frame 8-1000um flux, S(IR), to monochromatic radio flux, S(1.4GHz), for galaxies selected at far-IR and radio wavelengths, to search for signs that the ratio evolves with redshift, luminosity or dust temperature, and to identify any far-IR-bright outliers - useful laboratories for exploring why the far-IR/radio correlation is generally so tight when the prevailing theory suggests variations are almost inevitable. We use flux-limited 250-um and 1.4-GHz samples, obtained in GOODS-N using Herschel (HerMES; PEP) and the VLA. We determine bolometric IR output using ten bands spanning 24-1250um, exploiting data from PACS and SPIRE, as well as Spitzer, SCUBA, AzTEC and MAMBO. We also explore the properties of an L(IR)-matched sample, designed to reveal evolution of q(IR) with z, spanning log L(IR) = 11-12 L(sun) and z=0-2, by stacking into the radio and far-IR images. For 1.4-GHz-selected galaxies, we see tentative evidence of a break in the flux ratio, q(IR), at L(1...

  12. International Halley Watch: Discipline specialists for radio science

    Science.gov (United States)

    Irvine, W. M.; Schloerb, F. P.; Gerard, E.; Brown, R. D.; Godfrey, P.

    1986-01-01

    Some 34 radio observatories in 18 countries are participating in the Radio Science Net of the International Halley Watch. Approximately 100 radio astronomers are contributing to this effort, which has included observations of comets P/Crommelin and P/Giacobini-Zinner as well as P/Halley. It is clear that the record of data for the 18 cm OH ground state lambda doublet, which provides fundamental information on the gas production rate, kinematics, and potentially the magnetic field in the coma, will be vastly more complete and of higher accuracy than has even been obtained on any previous comet. The coverage by a number of radio observatories will enable short period variations to be studied and correlated with simultaneous data obtained at other wavelengths. Likewise, the first definitive detection of the important parent molecule hydrogen cyanide in a comet was obtained and is being studied by groups in the United States, Sweden, and France. The first detection of the comet with the Very Large Array telescope operated by NRAO was achieved and has produced exciting results for the distribution of emission at high angular resolution from the OH radical. At this writing data are still being obtained and being processed, and there are still strong indications that exciting information will be obtained from radar studies of P/Halley and from searches for additional parent molecules.

  13. Ulysses radio and plasma wave observations in the Jupiter environment

    Science.gov (United States)

    Stone, R. G.; Pedersen, B. M.; Harvey, C. C.; Canu, P.; Cornilleau-Wehrlin, N.; Desch, M. D.; De Villedary, C.; Fainberg, J.; Farrell, W. M.; Goetz, K.

    1992-01-01

    The Unified Radio and Plasma Wave (URAP) experiment has produced new observations of the Jupiter environment, owing to the unique capabilities of the instrument and the traversal of high Jovian latitudes. Broad-band continuum radio emission from Jupiter and in situ plasma waves have proved valuable in delineating the magnetospheric boundaries. Simultaneous measurements of electric and magnetic wave fields have yielded new evidence of whistler-mode radiation within the magnetosphere. Observations of auroral-like hiss provided evidence of a Jovian cusp. The source direction and polarization capabilities of URAP have demonstrated that the outer region of the Io plasma torus supported at least five separate radio sources that reoccurred during successive rotations with a measurable corotation lag. Thermal noise measurements of the Io torus densities yielded values in the densest portion that are similar to models suggested on the basis of Voyager observations of 13 years ago. The URAP measurements also suggest complex beaming and polarization characteristics of Jovian radio components. In addition, a new class of kilometer-wavelength striated Jovian bursts has been observed.

  14. Wavelength mismatch effect in electromagnetically induced absorption

    OpenAIRE

    Bharti, Vineet; Wasan, Ajay; Natarajan, Vasant

    2016-01-01

    We present a theoretical investigation of the phenomenon of electromagnetically induced absorption (EIA) in a 4-level system consisting of vee and ladder subsystems. The four levels are coupled using one weak probe field, and two strong control fields. We consider an experimental realization using energy levels of Rb. This necessitates dealing with different conditions of wavelength mismatch---near-perfect match where all three wavelengths are approximately equal; partial mismatch where the w...

  15. Long-wavelength VCSELs for sensing applications

    Science.gov (United States)

    Ortsiefer, M.; Rosskopf, J.; Neumeyr, C.; Gründl, T.; Grasse, C.; Chen, J.; Hangauer, A.; Strzoda, R.; Gierl, C.; Meissner, P.; Küppers, F.; Amann, M.-C.

    2012-03-01

    Long-wavelength VCSELs with emission wavelengths beyond 1.3 μm have seen a remarkable progress over the last decade. This success has been accomplished by using highly advanced device concepts which effectively overcome the fundamental technological drawbacks related with long-wavelength VCSELs such as inferior thermal properties and allow for the realization of lasers with striking device performance. In this presentation, we will give an overview on the state of the technology for long-wavelength VCSELs in conjunction with their opportunities in applications for optical sensing. While VCSELs based on InP are limited to maximum emission wavelengths around 2.3 μm, even longer wavelengths up to the mid-infrared range beyond 3 μm can be achieved with VCSELs based on GaSb. For near-infrared InP-based VCSELs, the output characteristics include sub-mA threshold currents, up to several milliwatts of singlemode output power and ultralow power consumption. New concepts for widely tunable VCSELs with tuning ranges up to 100 nm independent from the material system for the active region are also presented. Today, optical sensing by Tunable Diode Laser Spectroscopy is a fast emerging market. Gas sensing systems are used for a wide range of applications such as industrial process control, environmental monitoring and safety applications. With their inherent and compared to other laser types superior properties including enhanced current tuning rates, wavelength tuning ranges, modulation frequencies and power consumption, long-wavelength VCSELs are regarded as key components for TDLS applications.

  16. Principle analysis of IP wavelength router

    Institute of Scientific and Technical Information of China (English)

    王勇; 殷洪玺; 徐安士; 吴德明

    2001-01-01

    Combining IP with WDM is an attractive direction for research. WDM will play an important role in IP network in future. Now, an urgent problem is how to introduce wavelength routing in an IP network. We solve this problem by designing IP wavelength router, implementing DPDP (default path and dedicated path) method. We prove the reasonableness and feasibility of this design by a principle experiment. A lot of problems related to this design are also discussed.

  17. The faint radio sky: radio astronomy becomes mainstream

    CERN Document Server

    Padovani, Paolo

    2016-01-01

    Radio astronomy has changed. For years it studied relatively rare sources, which emit mostly non-thermal radiation across the entire electromagnetic spectrum, i.e. radio quasars and radio galaxies. Now it is reaching such faint flux densities that it detects mainly star-forming galaxies and the more common radio-quiet active galactic nuclei. These sources make up the bulk of the extragalactic sky, which has been studied for decades in the infrared, optical, and X-ray bands. I follow the transformation of radio astronomy by reviewing the main components of the radio sky at the bright and faint ends, the issue of their proper classification, their number counts, luminosity functions, and evolution. The overall "big picture" astrophysical implications of these results, and their relevance for a number of hot topics in extragalactic astronomy, are also discussed. The future prospects of the faint radio sky are very bright, as we will soon be flooded with survey data. This review should be useful to all extragalac...

  18. Long delayed radio echoes

    International Nuclear Information System (INIS)

    This thesis describes an experimental program carried out at Stanford over a five-year period. The experiment involved transmitting a radio signal, and tape-recording the output of a receiver gang-tuned with the transmitter for the following 30 s interval. The tapes were later audited for possible LDE. Although none of the possible LDE received reproduces exactly the transmitted signal, many exhibit features that seem unlikely to have been generated except by an LDE mechanism. A mechanism for producing LDE has been studied which involves signal propagation in an electron plasma wave mode at very low group velocity. Modifications to the simplified theory leading to prediction of longer delays are discussed

  19. Implementing Software Defined Radio

    CERN Document Server

    Grayver, Eugene

    2013-01-01

    Software Defined Radio makes wireless communications easier, more efficient, and more reliable. This book bridges the gap between academic research and practical implementation. When beginning a project, practicing engineers, technical managers, and graduate students can save countless hours by considering the concepts presented in these pages. The author covers the myriad options and trade-offs available when selecting an appropriate hardware architecture. As demonstrated here, the choice between hardware- and software-centric architecture can mean the difference between meeting an aggressive schedule and bogging down in endless design iterations. Because of the author’s experience overseeing dozens of failed and successful developments, he is able to present many real-life examples. Some of the key concepts covered are: Choosing the right architecture for the market – laboratory, military, or commercial Hardware platforms – FPGAs, GPPs, specialized and hybrid devices Standardization efforts to ens...

  20. Correlation radio range finder

    Directory of Open Access Journals (Sweden)

    A. Sorochan

    2012-10-01

    Full Text Available In work widely known methods of range measuring are short characterized. The basic attention is given features of signal processing in a correlation method of range measuring. The signal with angular modulation with one-voice-frequency fluctuation is used as a probing signal. The absence of Doppler effect on the formation of the correlation integral, the frequency instability of the transmitter, the phase change on reflection from the target is presented. It is noticed that the result of signal processing in the range measuring instrument is reduced to formation on an exit one-voice-frequency harmonious fluctuation equal to modulating frequency that provides high characteristics of a radio range finder.