Fossil shell emission in dying radio loud AGNs

Science.gov (United States)

Kino, M.; Ito, H.; Kawakatu, N.; Orienti, M.; Nagai, H.; Wajima, K.; Itoh, R.

2016-02-01

We investigate shell emission associated with dying radio loud AGNs. First, based on our recent work by Ito et al. (2015), we describe the dynamical and spectral evolution of shells after stopping the jet energy injection. We find that the shell emission overwhelms that of the radio lobes soon after stopping the jet energy injection because fresh electrons are continuously supplied into the shell via the forward shock, while the radio lobes rapidly fade out without jet energy injection. We find that such fossil shells can be a new class of target sources for SKA telescope. Next, we apply the model to the nearby radio source 3C84. Then, we find that the fossil shell emission in 3C84 is less luminous in the radio band while it is bright in the TeV γ-ray band and can be detectable by CTA. Data from STELLA

MASER: Measuring, Analysing, Simulating low frequency Radio Emissions.

Science.gov (United States)

Cecconi, B.; Le Sidaner, P.; Savalle, R.; Bonnin, X.; Zarka, P. M.; Louis, C.; Coffre, A.; Lamy, L.; Denis, L.; Griessmeier, J. M.; Faden, J.; Piker, C.; André, N.; Genot, V. N.; Erard, S.; King, T. A.; Mafi, J. N.; Sharlow, M.; Sky, J.; Demleitner, M.

2017-12-01

The MASER (Measuring, Analysing and Simulating Radio Emissions) project provides a comprehensive infrastructure dedicated to low frequency radio emissions (typically Radioastronomie de Nançay and the CDPP deep archive. These datasets include Cassini/RPWS, STEREO/Waves, WIND/Waves, Ulysses/URAP, ISEE3/SBH, Voyager/PRA, Nançay Decameter Array (Routine, NewRoutine, JunoN), RadioJove archive, swedish Viking mission, Interball/POLRAD... MASER also includes a Python software library for reading raw data.

Extended Radio Emission in MOJAVE Blazars: Challenges to Unification

Science.gov (United States)

Kharb, P.; Lister, M. L.; Cooper, N. J.

2010-02-01

We present the results of a study on the kiloparsec-scale radio emission in the complete flux density limited MOJAVE sample, comprising 135 radio-loud active galactic nuclei. New 1.4 GHz Very Large Array (VLA) radio images of six quasars and previously unpublished images of 21 blazars are presented, along with an analysis of the high-resolution (VLA A-array) 1.4 GHz emission for the entire sample. While extended emission is detected in the majority of the sources, about 7% of the sources exhibit only radio core emission. We expect more sensitive radio observations, however, to detect faint emission in these sources, as we have detected in the erstwhile "core-only" source, 1548+056. The kiloparsec-scale radio morphology varies widely across the sample. Many BL Lac objects exhibit extended radio power and kiloparsec-scale morphology typical of powerful FRII jets, while a substantial number of quasars possess radio powers intermediate between FRIs and FRIIs. This poses challenges to the simple radio-loud unified scheme, which links BL Lac objects to FRIs and quasars to FRIIs. We find a significant correlation between extended radio emission and parsec-scale jet speeds: the more radio powerful sources possess faster jets. This indicates that the 1.4 GHz (or low-frequency) radio emission is indeed related to jet kinetic power. Various properties such as extended radio power and apparent parsec-scale jet speeds vary smoothly between different blazar subclasses, suggesting that, at least in terms of radio jet properties, the distinction between quasars and BL Lac objects, at an emission-line equivalent width of 5 Å, is essentially an arbitrary one. While the two blazar subclasses display a smooth continuation in properties, they often reveal differences in the correlation test results when considered separately. This can be understood if, unlike quasars, BL Lac objects do not constitute a homogeneous population, but rather include both FRI and FRII radio galaxies for

EXTENDED RADIO EMISSION IN MOJAVE BLAZARS: CHALLENGES TO UNIFICATION

International Nuclear Information System (INIS)

Kharb, P.; Lister, M. L.; Cooper, N. J.

2010-01-01

We present the results of a study on the kiloparsec-scale radio emission in the complete flux density limited MOJAVE sample, comprising 135 radio-loud active galactic nuclei. New 1.4 GHz Very Large Array (VLA) radio images of six quasars and previously unpublished images of 21 blazars are presented, along with an analysis of the high-resolution (VLA A-array) 1.4 GHz emission for the entire sample. While extended emission is detected in the majority of the sources, about 7% of the sources exhibit only radio core emission. We expect more sensitive radio observations, however, to detect faint emission in these sources, as we have detected in the erstwhile 'core-only' source, 1548+056. The kiloparsec-scale radio morphology varies widely across the sample. Many BL Lac objects exhibit extended radio power and kiloparsec-scale morphology typical of powerful FRII jets, while a substantial number of quasars possess radio powers intermediate between FRIs and FRIIs. This poses challenges to the simple radio-loud unified scheme, which links BL Lac objects to FRIs and quasars to FRIIs. We find a significant correlation between extended radio emission and parsec-scale jet speeds: the more radio powerful sources possess faster jets. This indicates that the 1.4 GHz (or low-frequency) radio emission is indeed related to jet kinetic power. Various properties such as extended radio power and apparent parsec-scale jet speeds vary smoothly between different blazar subclasses, suggesting that, at least in terms of radio jet properties, the distinction between quasars and BL Lac objects, at an emission-line equivalent width of 5 A, is essentially an arbitrary one. While the two blazar subclasses display a smooth continuation in properties, they often reveal differences in the correlation test results when considered separately. This can be understood if, unlike quasars, BL Lac objects do not constitute a homogeneous population, but rather include both FRI and FRII radio galaxies for

Affirmation of triggered Jovian radio emissions and their attribution to corotating radio lasers

Science.gov (United States)

Calvert, W.

1985-01-01

It is argued that the original statistical evidence for the existence of triggered radio emissions and corotating radio lasers on Jupiter remains valid notwithstanding the critique of Desch and Kaiser (1985). The Voyager radio spectrograms used to identify the triggered emissions are analyzed and the results are discussed. It is shown that the critique by Desch and Kaiser is unjustified because it is not based on the original event criteria, i.e., the correlation between the occurrence of Jovian auroral kilometric radiation and fast-drift type III solar bursts in the same frequency.

Multifrequency VLA observations of PKS 0745-191: the archetypal 'cooling flow' radio source?

International Nuclear Information System (INIS)

Baum, S.A.; O'Dea, C.P.

1991-01-01

We present 90-, 20-, 6- and 2-cm VLA observations of the high radio luminosity, cooling flow radio source PKS 0745-191. We find that the radio source has a core with a very steep spectrum and diffuse emission with an even steeper spectrum without clear indications of the jets, hotspots or double lobes found in other radio sources of comparable luminosity. The appearance of the source is highly dependent on frequency and resolution. This dependence reflects both the diffuse nature of the extended emission and the steep, but position-dependent, spectrum of the radio emission. (author)

Cross-Correlations in Quasar Radio Emission

Science.gov (United States)

Nefedyev, Yuri; Panischev, Oleg; Demin, Sergey

The main factors forming the complex evolution of the accretive astrophysical systems are nonlinearity, intermittency, nonstationarity and also collective phenomena. To discover the dynamic processes in these objects and to detain understanding their properties we need to use all the applicable analyzing methods. Here we use the Flicker-Noise Spectroscopy (FNS) as a phenomenological approach to analyzing and parameterizing the auto- and cross-correlations in time series of astrophysical objects dynamics. As an example we consider the quasar flux radio spectral density at frequencies 2.7 GHz and 8.1 GHz. Data have been observed by Dr. N. Tanizuka (Laboratory for Complex Systems Analysis, Osaka Prefecture University) in a period of 1979 to 1988 (3 309 days). According to mental habits quasar is a very energetic and distant active galactic nucleus containing a supermassive black hole by size 10-10,000 times the Schwarzschild radius. The quasar is powered by an accretion disc around the black hole. The accretion disc material layers, moving around the black hole, are under the influence of gravitational and frictional forces. It results in raising the high temperature and arising the resonant and collective phenomena reflected in quasar emission dynamics. Radio emission dynamics of the quasar 0215p015 is characterized by three quasi-periodic processes, which are prevalent in considering dynamics. By contrast the 1641p399's emission dynamics have not any distinguish processes. It means the presence of high intermittency in accretive modes. The second difference moment allows comparing the degree of manifesting of resonant and chaotic components in initial time series of the quasar radio emission. The comparative analysis shows the dominating of chaotic part of 1641p399's dynamics whereas the radio emission of 0215p015 has the predominance of resonant component. Analyzing the collective features of the quasar radio emission intensity demonstrates the significant

GMRT Low Radio Frequency Study of the Wolf Rayet Galaxy NGC ...

Indian Academy of Sciences (India)

In this paper, we present the first low frequency (< 1.4 GHz) radio continuum study of a Wolf Rayet galaxy NGC 4214 using the Giant Meterwave Radio Telescope (GMRT). We detect diffuse extended emission from the galaxy disk at 325 MHz and find that the radio emission closely follows the ultraviolet emission mapped by ...

Mean and Extreme Radio Properties of Quasars and the Origin of Radio Emission

Science.gov (United States)

Richards, Gordon T.; Kratzer, R.

2014-01-01

We explore the evolution of the fraction of radio loud quasars and the mean radio properties of quasars. Although any quasar has only a ~10% chance of being radio loud and the average quasar has a radio luminosity of ~4x10^30 ergs/s/Hz, these properties are strong functions of not only luminosity, redshift, black hole mass, and accretion rate, but also the strength of the accretion disk wind (as characterized by CIV emission line properties). Quasars with higher optical luminosity and/or lower redshift have a higher than average probability of being radio loud, but their median radio luminosity (relative to optical) is much lower than average. We find that, while radio properties of quasars generally cannot be predicted from their optical properties, objects where one expects a strong radiation line driven wind (based on emission line features) have virtually no chance of being radio loud. The redder quasars are in the optical, the more radio flux (relative to optical) they have; this trend holds even for quasars that are not expected to be significantly dust reddened/extincted in the optical. Finally, we consider the radio properties of quasars in the framework of models which describe the radio loud extrema as being due to particularly high spin resulting from second generation mergers and in the context of star formation at lower levels of radio flux. This work was supported by NSF AAG grant 1108798.

RESOLVE: A new algorithm for aperture synthesis imaging of extended emission in radio astronomy

Science.gov (United States)

Junklewitz, H.; Bell, M. R.; Selig, M.; Enßlin, T. A.

2016-02-01

We present resolve, a new algorithm for radio aperture synthesis imaging of extended and diffuse emission in total intensity. The algorithm is derived using Bayesian statistical inference techniques, estimating the surface brightness in the sky assuming a priori log-normal statistics. resolve estimates the measured sky brightness in total intensity, and the spatial correlation structure in the sky, which is used to guide the algorithm to an optimal reconstruction of extended and diffuse sources. During this process, the algorithm succeeds in deconvolving the effects of the radio interferometric point spread function. Additionally, resolve provides a map with an uncertainty estimate of the reconstructed surface brightness. Furthermore, with resolve we introduce a new, optimal visibility weighting scheme that can be viewed as an extension to robust weighting. In tests using simulated observations, the algorithm shows improved performance against two standard imaging approaches for extended sources, Multiscale-CLEAN and the Maximum Entropy Method.

VERY LONG BASELINE ARRAY IMAGING OF PARSEC-SCALE RADIO EMISSIONS IN NEARBY RADIO-QUIET NARROW-LINE SEYFERT 1 GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Doi, Akihiro [The Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuou-ku, Sagamihara, Kanagawa 252-5210 (Japan); Asada, Keiichi; Inoue, Makoto [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China); Fujisawa, Kenta [The Research Institute of Time Studies, Yamaguchi University, 1677-1 Yoshida, Yamaguchi, Yamaguchi 753-8511 (Japan); Nagai, Hiroshi; Hagiwara, Yoshiaki [National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Wajima, Kiyoaki, E-mail: akihiro.doi@vsop.isas.jaxa.jp [Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030 (China)

2013-03-01

We conducted Very Long Baseline Array (VLBA) observations of seven nearby narrow-line Seyfert 1 (NLS1) galaxies at 1.7 GHz ({lambda}18 cm) with milliarcsecond resolution. This is the first systematic very long baseline interferometry study focusing on the central parsec-scale regions of radio-quiet NLS1s. Five of the seven were detected at a brightness temperature of {approx}> 5 Multiplication-Sign 10{sup 6} K and contain radio cores with high brightness temperatures of >6 Multiplication-Sign 10{sup 7} K, indicating a nonthermal process driven by jet-producing central engines as in radio-loud NLS1s and other active galactic nucleus classes. VLBA images of MRK 1239, MRK 705, and MRK 766 exhibit parsec-scale jets with clear linear structures. A large portion of the radio power comes from diffuse emission components that are distributed within the nuclear regions ({approx}< 300 pc), which is a common characteristic throughout the observed NLS1s. Jet kinetic powers limited by the Eddington limit may be insufficient to allow the jets to escape to kiloparsec scales for these radio-quiet NLS1s with low-mass black holes of {approx}< 10{sup 7} M {sub Sun }.

Radio emission in the Virgo cluster and in SO galaxies

International Nuclear Information System (INIS)

Kotanyi, C.

1981-01-01

A survey of the radio continuum emission from the galaxies in the Virgo Cluster is presented. The sample of 274 galaxies in total contains a subsample of 188 galaxies complete down to magntiude msub(p) = 14. The observations consisted mostly of short (10 minutes) observations providing one-dimensional (East-West) strip distributions of the radio brightness at 1.4 GHz, with an East-West resolution of 23'' allowing separation of central sources from extended emission, and an r.m.s. noise level of 2 mJy. The radio emission of SO galaxies is examined. A sample of 145 SO galaxies is obtained by combining the Virgo cluster SO's with the nearby non-cluster SO's. The radio data, mainly from short observations, are used to derive the RLF. The radio emission in SO galaxies is at least three times weaker than that in ellipticals and spirals. Flat-spectrum compact nuclear sources are found in SO galaxies but they are at least 10 times weaker than in elliptical galaxies, which is attributed to the small mass of the bulges in SO's as compared to the mass of elliptical galaxies. The absence of steep-spectrum, extended central sources and of disk radio emission in SO's is attributed to their low neutral hydrogen content. (Auth.)

Discovery of a radio nebula around PSR J0855-4644

Science.gov (United States)

Maitra, C.; Roy, S.; Acero, F.; Gupta, Y.

2018-03-01

We report the discovery of a diffuse radio emission around PSR J0855-4644 using an upgraded GMRT (uGMRT) observation at 1.35 GHz. The radio emission is spatially coincident with the diffuse X-ray pulsar wind nebula (PWN) seen with XMM-Newton but is much larger in extent compared to the compact axisymmetric PWN seen with Chandra. The morphology of the emission, with a bright partial ring-like structure and two faint tail-like features strongly resembles a bow shock nebula, and indicates a velocity of 100 km/s through the ambient medium. We conclude that the emission is most likely to be associated with the radio PWN of PSR J0855-4644. From the integrated flux density, we estimate the energetics of the PWN.

LOFAR discovery of a double radio halo system in Abell 1758 and radio/X-ray study of the cluster pair

Science.gov (United States)

Botteon, A.; Shimwell, T. W.; Bonafede, A.; Dallacasa, D.; Brunetti, G.; Mandal, S.; van Weeren, R. J.; Brüggen, M.; Cassano, R.; de Gasperin, F.; Hoang, D. N.; Hoeft, M.; Röttgering, H. J. A.; Savini, F.; White, G. J.; Wilber, A.; Venturi, T.

2018-05-01

Radio halos and radio relics are diffuse synchrotron sources that extend over Mpc-scales and are found in a number of merger galaxy clusters. They are believed to form as a consequence of the energy that is dissipated by turbulence and shocks in the intra-cluster medium (ICM). However, the precise physical processes that generate these steep synchrotron spectrum sources are still poorly constrained. We present a new LOFAR observation of the double galaxy cluster Abell 1758. This system is composed of A1758N, a massive cluster hosting a known giant radio halo, and A1758S, which is a less massive cluster whose diffuse radio emission is confirmed here for the first time. Our observations have revealed a radio halo and a candidate radio relic in A1758S, and a suggestion of emission along the bridge connecting the two systems which deserves confirmation. We combined the LOFAR data with archival VLA and GMRT observations to constrain the spectral properties of the diffuse emission. We also analyzed a deep archival Chandra observation and used this to provide evidence that A1758N and A1758S are in a pre-merger phase. The ICM temperature across the bridge that connects the two systems shows a jump which might indicate the presence of a transversal shock generated in the initial stage of the merger.

A possible mechanism for the pulsar radio emission

International Nuclear Information System (INIS)

Hinata, S.

1977-01-01

The possibility of radio emission is considered within a model which produces the beam-plasma system near the pulsar. A longitudinal instability develops near the light cylinder for a particular choice of parameters adopted in the paper. The excited wave strongly oscillates the beam particles perpendicular to its average velocity on one hand, and forms bunches of them on the other hand. Consequently, coherent radiation is expected. The frequency of the emission falls within the radio band, but the intensity turns out to be too low to explain observations. An appreciable enhancement of the beam number density over the Goldreich-Julian value (nsub(b) approximately equal to BΩ/2πec) is needed if the mechanism discussed in the present paper is responsible for the pulsar radio emission. (Auth.)

Observations of a nearby filament of galaxy clusters with the Sardinia Radio Telescope

Science.gov (United States)

Vacca, Valentina; Murgia, M.; Loi, F. Govoni F.; Vazza, F.; Finoguenov, A.; Carretti, E.; Feretti, L.; Giovannini, G.; Concu, R.; Melis, A.; Gheller, C.; Paladino, R.; Poppi, S.; Valente, G.; Bernardi, G.; Boschin, W.; Brienza, M.; Clarke, T. E.; Colafrancesco, S.; Enßlin, T.; Ferrari, C.; de Gasperin, F.; Gastaldello, F.; Girardi, M.; Gregorini, L.; Johnston-Hollitt, M.; Junklewitz, H.; Orrù, E.; Parma, P.; Perley, R.; Taylor, G. B.

2018-05-01

We report the detection of diffuse radio emission which might be connected to a large-scale filament of the cosmic web covering a 8° × 8° area in the sky, likely associated with a z≈0.1 over-density traced by nine massive galaxy clusters. In this work, we present radio observations of this region taken with the Sardinia Radio Telescope. Two of the clusters in the field host a powerful radio halo sustained by violent ongoing mergers and provide direct proof of intra-cluster magnetic fields. In order to investigate the presence of large-scale diffuse radio synchrotron emission in and beyond the galaxy clusters in this complex system, we combined the data taken at 1.4 GHz with the Sardinia Radio Telescope with higher resolution data taken with the NRAO VLA Sky Survey. We found 28 candidate new sources with a size larger and X-ray emission fainter than known diffuse large-scale synchrotron cluster sources for a given radio power. This new population is potentially the tip of the iceberg of a class of diffuse large-scale synchrotron sources associated with the filaments of the cosmic web. In addition, we found in the field a candidate new giant radio galaxy.

Radio emission from embryonic superluminous supernova remnants

Science.gov (United States)

Omand, Conor M. B.; Kashiyama, Kazumi; Murase, Kohta

2018-02-01

It has been widely argued that Type-I superluminous supernovae (SLSNe-I) are driven by powerful central engines with a long-lasting energy injection after the core-collapse of massive progenitors. One of the popular hypotheses is that the hidden engines are fast-rotating pulsars with a magnetic field of B ˜ 1013-1015 G. Murase, Kashiyama & Mészáros proposed that quasi-steady radio/submm emission from non-thermal electron-positron pairs in nascent pulsar wind nebulae can be used as a relevant counterpart of such pulsar-driven supernovae (SNe). In this work, focusing on the nascent SLSN-I remnants, we examine constraints that can be placed by radio emission. We show that the Atacama Large Millimeter/submillimetre Array can detect the radio nebula from SNe at DL ˜ 1 Gpc in a few years after the explosion, while the Jansky Very Large Array can also detect the counterpart in a few decades. The proposed radio follow-up observation could solve the parameter degeneracy in the pulsar-driven SN model for optical/UV light curves, and could also give us clues to young neutron star scenarios for SLSNe-I and fast radio bursts.

GMRT Low Radio Frequency Study of the Wolf Rayet Galaxy NGC ...

Indian Academy of Sciences (India)

Abstract. In this paper, we present the first low frequency (< 1.4 GHz) radio continuum study of a Wolf Rayet galaxy NGC 4214 using the. Giant Meterwave Radio Telescope (GMRT). We detect diffuse extended emission from the galaxy disk at 325 MHz and find that the radio emis- sion closely follows the ultraviolet emission ...

Mean and extreme radio properties of quasars and the origin of radio emission

Energy Technology Data Exchange (ETDEWEB)

Kratzer, Rachael M.; Richards, Gordon T. [Department of Physics, Drexel University, Philadelphia, PA (United States)

2015-02-01

We investigate the evolution of both the radio-loud fraction (RLF) and (using stacking analysis) the mean radio loudness of quasars. We consider how these properties evolve as a function of redshift and luminosity, black hole (BH) mass and accretion rate, and parameters related to the dominance of a wind in the broad emission-line region. We match the FIRST source catalog to samples of luminous quasars (both spectroscopic and photometric), primarily from the Sloan Digital Sky Survey. After accounting for catastrophic errors in BH mass estimates at high redshift, we find that both the RLF and the mean radio luminosity increase for increasing BH mass and decreasing accretion rate. Similarly, both the RLF and mean radio loudness increase for quasars that are argued to have weaker radiation line driven wind components of the broad emission-line region. In agreement with past work, we find that the RLF increases with increasing optical/UV luminosity and decreasing redshift, while the mean radio loudness evolves in the exact opposite manner. This difference in behavior between the mean radio loudness and the RLF in L−z may indicate selection effects that bias our understanding of the evolution of the RLF; deeper surveys in the optical and radio are needed to resolve this discrepancy. Finally, we argue that radio-loud (RL) and radio-quiet (RQ) quasars may be parallel sequences, but where only RQ quasars at one extreme of the distribution are likely to become RL, possibly through slight differences in spin and/or merger history.

Fast Radio Bursts’ Emission Mechanism: Implication from Localization

Energy Technology Data Exchange (ETDEWEB)

Lyutikov, Maxim [Department of Physics and Astronomy, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907-2036 (United States)

2017-03-20

We argue that the localization of the repeating fast radio bursts (FRBs) at ∼1 Gpc excludes a rotationally powered type of radio emission (e.g., analogs of Crab’s giant pulses coming from very young energetic pulsars) as the origin of FRBs.

Fast Radio Bursts’ Emission Mechanism: Implication from Localization

International Nuclear Information System (INIS)

Lyutikov, Maxim

2017-01-01

We argue that the localization of the repeating fast radio bursts (FRBs) at ∼1 Gpc excludes a rotationally powered type of radio emission (e.g., analogs of Crab’s giant pulses coming from very young energetic pulsars) as the origin of FRBs.

ATCA observations of the MACS-Planck Radio Halo Cluster Project. II. Radio observations of an intermediate redshift cluster sample

Science.gov (United States)

Martinez Aviles, G.; Johnston-Hollitt, M.; Ferrari, C.; Venturi, T.; Democles, J.; Dallacasa, D.; Cassano, R.; Brunetti, G.; Giacintucci, S.; Pratt, G. W.; Arnaud, M.; Aghanim, N.; Brown, S.; Douspis, M.; Hurier, J.; Intema, H. T.; Langer, M.; Macario, G.; Pointecouteau, E.

2018-04-01

Aim. A fraction of galaxy clusters host diffuse radio sources whose origins are investigated through multi-wavelength studies of cluster samples. We investigate the presence of diffuse radio emission in a sample of seven galaxy clusters in the largely unexplored intermediate redshift range (0.3 http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/611/A94

On the relationship between optical and radio emission from active galaxy nuclei

International Nuclear Information System (INIS)

Zentsova, A.S.; Fedorenko, V.N.

1991-01-01

Model in which the radio emission of nuclei of Seyfert galaxies emerges in the regions of formation of their narrow emission lines, R∼100 pc is developed. Gaseous clouds, producing this emission, are moving in the surrounding hot gas and induce shock waves. The shock waves accelerate electrons, which produce radio emission via synchrotron mechanism. The model explains an observational correlation between the radio and optical properties of Seyfert galaxies and makes some predictions on the parameters of the region R∼100 pc

Kinetic Simulations of Type II Radio Burst Emission Processes

Science.gov (United States)

Ganse, U.; Spanier, F. A.; Vainio, R. O.

2011-12-01

The fundamental emission process of Type II Radio Bursts has been under discussion for many decades. While analytic deliberations point to three wave interaction as the source for fundamental and harmonic radio emissions, sparse in-situ observational data and high computational demands for kinetic simulations have not allowed for a definite conclusion to be reached. A popular model puts the radio emission into the foreshock region of a coronal mass ejection's shock front, where shock drift acceleration can create eletrcon beam populations in the otherwise quiescent foreshock plasma. Beam-driven instabilities are then assumed to create waves, forming the starting point of three wave interaction processes. Using our kinetic particle-in-cell code, we have studied a number of emission scenarios based on electron beam populations in a CME foreshock, with focus on wave-interaction microphysics on kinetic scales. The self-consistent, fully kinetic simulations with completely physical mass-ratio show fundamental and harmonic emission of transverse electromagnetic waves and allow for detailled statistical analysis of all contributing wavemodes and their couplings.

A model for radio emission from solar coronal shocks

Energy Technology Data Exchange (ETDEWEB)

Zhao, G. Q.; Chen, L.; Wu, D. J., E-mail: djwu@pmo.ac.cn [Purple Mountain Observatory, CAS, Nanjing 210008 (China)

2014-05-01

Solar coronal shocks are very common phenomena in the solar atmosphere and are believed to be the drivers of solar type II radio bursts. However, the microphysical nature of these emissions is still an open question. This paper proposes that electron cyclotron maser (ECM) emission is responsible for the generation of radiation from the coronal shocks. In the present model, an energetic ion beam accelerated by the shock first excites the Alfvén wave (AW), then the excited AW leads to the formation of a density-depleted duct along the foreshock boundary of the shock. In this density-depleted duct, the energetic electron beam produced via the shock acceleration can effectively excite radio emission by ECM instability. Our results show that this model may potentially be applied to solar type II radio bursts.

A model for radio emission from solar coronal shocks

International Nuclear Information System (INIS)

Zhao, G. Q.; Chen, L.; Wu, D. J.

2014-01-01

Solar coronal shocks are very common phenomena in the solar atmosphere and are believed to be the drivers of solar type II radio bursts. However, the microphysical nature of these emissions is still an open question. This paper proposes that electron cyclotron maser (ECM) emission is responsible for the generation of radiation from the coronal shocks. In the present model, an energetic ion beam accelerated by the shock first excites the Alfvén wave (AW), then the excited AW leads to the formation of a density-depleted duct along the foreshock boundary of the shock. In this density-depleted duct, the energetic electron beam produced via the shock acceleration can effectively excite radio emission by ECM instability. Our results show that this model may potentially be applied to solar type II radio bursts.

A search for radio emission from exoplanets around evolved stars

Science.gov (United States)

O'Gorman, E.; Coughlan, C. P.; Vlemmings, W.; Varenius, E.; Sirothia, S.; Ray, T. P.; Olofsson, H.

2018-04-01

The majority of searches for radio emission from exoplanets have to date focused on short period planets, i.e., the so-called hot Jupiter type planets. However, these planets are likely to be tidally locked to their host stars and may not generate sufficiently strong magnetic fields to emit electron cyclotron maser emission at the low frequencies used in observations (typically ≥150 MHz). In comparison, the large mass-loss rates of evolved stars could enable exoplanets at larger orbital distances to emit detectable radio emission. Here, we first show that the large ionized mass-loss rates of certain evolved stars relative to the solar value could make them detectable with the LOw Frequency ARray (LOFAR) at 150 MHz (λ = 2 m), provided they have surface magnetic field strengths >50 G. We then report radio observations of three long period (>1 au) planets that orbit the evolved stars β Gem, ι Dra, and β UMi using LOFAR at 150 MHz. We do not detect radio emission from any system but place tight 3σ upper limits of 0.98, 0.87, and 0.57 mJy on the flux density at 150 MHz for β Gem, ι Dra, and β UMi, respectively. Despite our non-detections these stringent upper limits highlight the potential of LOFAR as a tool to search for exoplanetary radio emission at meter wavelengths.

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...

Unification in the low radio luminosity regime: evidence from optical line emission

Science.gov (United States)

Marchã, M. J. M.; Browne, I. W. A.; Jethava, N.; Antón, S.

2005-08-01

We address the question of whether or not the properties of all low-luminosity flat spectrum radio sources, not just the obvious BL Lac objects, are consistent with them being the relativistically beamed counterparts of the low radio luminosity radio galaxies (the Fanaroff-Riley type 1, FR I). We have accumulated data on a well-defined sample of low redshift, core-dominated, radio sources all of which have one-sided core-jet structures seen with very long baseline interferometry, just like most BL Lac objects. We first compare the emission-line luminosities of the sample of core-dominated radio sources with a matched sample of FR I radio galaxies. The emission lines in the core-dominated objects are on average significantly more luminous than those in the comparison sample, inconsistent with the simplest unified models in which there is no orientation dependence of the line emission. We then compare the properties of our core-dominated sample with those of a sample of radio-emitting UGC galaxies selected without bias to core strength. The core-dominated objects fit well on the UGC correlation between line emission and radio core strength found by Verdoes Kleijn et al. The results are not consistent with all the objects participating in a simple unified model in which the observed line emission is orientation independent, though they could fit a single, unified model provided that some FR I radio galaxies have emission line regions that become more visible when viewed along the jet axis. However, they are equally consistent with a scenario in which, for the majority of objects, beaming has minimal effect on the observed core luminosities of a large fraction of the FR I population and that intrinsically stronger cores simply give rise to stronger emission lines. We conclude that FR I unification is much more complex than usually portrayed, and models combining beaming with an intrinsic relationship between core and emission line strengths need to be explored.

GAMMA-RAY BURST REVERSE SHOCK EMISSION IN EARLY RADIO AFTERGLOWS

Energy Technology Data Exchange (ETDEWEB)

Resmi, Lekshmi [Indian Institute of Space Science and Technology, Trivandrum (India); Zhang, Bing, E-mail: l.resmi@iist.ac.in [Department of Physics and Astronomy, University of Nevada, Las Vegas (United States)

2016-07-01

Reverse shock (RS) emission from gamma-ray bursts is an important tool in investigating the nature of the ejecta from the central engine. If the magnetization of the ejecta is not high enough to suppress the RS, a strong RS emission component, usually peaking in the optical/IR band early on, would provide an important contribution to early afterglow light curve. In the radio band, synchrotron self-absorption may suppress early RS emission and also delay the RS peak time. In this paper, we calculate the self-absorbed RS emission in the radio band under different dynamical conditions. In particular, we stress that the RS radio emission is subject to self-absorption in both RSs and forward shocks (FSs). We calculate the ratio between the RS to FS flux at the RS peak time for different frequencies, which is a measure of the detectability of the RS emission component. We then constrain the range of physical parameters for a detectable RS, in particular the role of magnetization. We notice that unlike optical RS emission which is enhanced by moderate magnetization, moderately magnetized ejecta do not necessarily produce a brighter radio RS due to the self-absorption effect. For typical parameters, the RS emission component would not be detectable below 1 GHz unless the medium density is very low (e.g., n < 10{sup −3} cm{sup −3} for the interstellar medium and A {sub *} < 5 × 10{sup −4} for wind). These predictions can be tested using the afterglow observations from current and upcoming radio facilities such as the Karl G. Jansky Very Large Array, the Low-Frequency Array, the Five Hundred Meter Aperture Spherical Telescope, and the Square Kilometer Array.

Radio search for pulsed emission from X-ray pulsars

Energy Technology Data Exchange (ETDEWEB)

delli Santi, F S; Delpino, F [Bologna Univ. (Italy). Ist. di Astronomia; Inzani, P; Sironi, G [Consiglio Nazionale delle Ricerche, Milan (Italy). Lab. di Fisica Cosmica e Tecnologie Relative; Mandolesi, N; Morigi, G [Consiglio Nazionale delle Ricerche, Bologna (Italy). Lab. TESRE

1981-05-01

An experiment has been performed at 325 MHz, with a 10 m tracking dish, for the search of pulsed radio emission associated with X-ray pulsars. No evidence of radio pulses has been found in the four sources investigated, although the radio pulsar PSR 0329 + 54, used a testing object, has been detected successfully.

The Relationship Between Solar Radio and Hard X-Ray Emission

Science.gov (United States)

White, S. M.; Benz, A. O.; Christe, S.; Farnik, F.; Kundu, M. R.; Mann, G.; Ning, Z.; Raulin, J.-P.; Silva-Valio, A. V. R.; Saint-Hilaire, P.;

QUASI-QUIESCENT RADIO EMISSION FROM THE FIRST RADIO-EMITTING T DWARF

Energy Technology Data Exchange (ETDEWEB)

Williams, Peter K. G.; Berger, Edo; Zauderer, B. Ashley, E-mail: pwilliams@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2013-04-20

Radio detections of ultracool dwarfs provide insight into their magnetic fields and the dynamos that maintain them, especially at the very bottom of the main sequence, where other activity indicators dramatically weaken. Until recently, radio emission was only detected in the M and L dwarf regimes, but this has changed with the Arecibo detection of rapid polarized flares from the T6.5 dwarf 2MASS J10475385+2124234. Here, we report the detection of quasi-quiescent radio emission from this source at 5.8 GHz using the Karl G. Jansky Very Large Array. The spectral luminosity is L{sub {nu}} = (2.2 {+-} 0.7) Multiplication-Sign 10{sup 12} erg s{sup -1} Hz{sup -1}, a factor of {approx}100 times fainter than the Arecibo flares. Our detection is the lowest luminosity yet achieved for an ultracool dwarf. Although the emission is fully consistent with being steady, unpolarized, and broad band, we find tantalizing hints for variability. We exclude the presence of short-duration flares as seen by Arecibo, although this is not unexpected given estimates of the duty cycle. Follow-up observations of this object will offer the potential to constrain its rotation period, electron density, and the strength and configuration of the magnetic field. Equally important, follow-up observations will address the question of whether the electron cyclotron maser instability, which is thought to produce the flares seen by Arecibo, also operates in the very different parameter regime of the emission we detect, or whether instead this ultracool dwarf exhibits both maser and gyrosynchrotron radiation, potentially originating from substantially different locations.

A GIANT RADIO HALO IN THE MASSIVE AND MERGING CLUSTER ABELL 1351

International Nuclear Information System (INIS)

Giacintucci, S.; Venturi, T.; Cassano, R.; Dallacasa, D.; Brunetti, G.

2009-01-01

We report on the detection of diffuse radio emission in the X-ray luminous and massive galaxy cluster A 1351 (z = 0.322) using archival Very Large Array data at 1.4 GHz. Given its central location, morphology, and Mpc-scale extent, we classify the diffuse source as a giant radio halo. X-ray and weak lensing studies show A 1351 to be a system undergoing a major merger. The halo is associated with the most massive substructure. The presence of this source is explained assuming that merger-driven turbulence may re-accelerate high-energy particles in the intracluster medium and generate diffuse radio emission on the cluster scale. The position of A 1351 in the log P 1.4GHz -log L X plane is consistent with that of all other radio-halo clusters known to date, supporting a causal connection between the unrelaxed dynamical state of massive (>10 15 M sun ) clusters and the presence of giant radio halos.

The statistics of radio emission from quasars

International Nuclear Information System (INIS)

Peacock, J.A.; Miller, L.; Longair, M.S.; Edinburgh Univ.

1986-01-01

The radio properties of quasars have traditionally been discussed in terms of the radio-to-optical flux-density ratio R, implying a correlation between emission in these wavebands. It is here shown that, for bright quasars, this apparent correlation is largely due to an abrupt change in the radio properties of the quasar population near absolute magnitude Msub(B)=-24. It is suggested that this change in due to the existence of two classes of quasar with differing host galaxies: a proportion of quasars brighter than Msub(B)approx.=-24 lie in elliptical galaxies and thus generate powerful radio sources, while elliptical galaxies with weaker nuclear quasar components are classified as N-galaxies rather than quasars; quasars fainter than Msub(B)approx.=-24 lie in spiral galaxies and thus are high-luminosity analogues of radio-quiet Seyfert galaxies. (author)

The air shower maximum probed by Cherenkov effects from radio emission

NARCIS (Netherlands)

de Vries, Krijn D.; Scholten, Olaf; Werner, Klaus

Radio detection of cosmic-ray-induced air showers has come to a flight the last decade. Along with the experimental efforts, several theoretical models were developed. The main radio-emission mechanisms are established to be the geomagnetic emission due to deflection of electrons and positrons in

Solar energetic particles and radio burst emission

Directory of Open Access Journals (Sweden)

Miteva Rositsa

2017-01-01

Full Text Available We present a statistical study on the observed solar radio burst emission associated with the origin of in situ detected solar energetic particles. Several proton event catalogs in the period 1996–2016 are used. At the time of appearance of the particle origin (flare and coronal mass ejection we identified radio burst signatures of types II, III and IV by inspecting dynamic radio spectral plots. The information from observatory reports is also accounted for during the analysis. The occurrence of solar radio burst signatures is evaluated within selected wavelength ranges during the solar cycle 23 and the ongoing 24. Finally, we present the burst occurrence trends with respect to the intensity of the proton events and the location of their solar origin.

Radio emission region exposed: courtesy of the double pulsar

Science.gov (United States)

Lomiashvili, David; Lyutikov, Maxim

2014-06-01

The double pulsar system PSR J0737-3039A/B offers exceptional possibilities for detailed probes of the structure of the pulsar magnetosphere, pulsar winds and relativistic reconnection. We numerically model the distortions of the magnetosphere of pulsar B by the magnetized wind from pulsar A, including effects of magnetic reconnection and of the geodetic precession. Geodetic precession leads to secular evolution of the geometric parameters and effectively allows a 3D view of the magnetosphere. Using the two complimentary models of pulsar B's magnetosphere, adapted from the Earth's magnetosphere models by Tsyganenko (ideal pressure confinement) and Dungey (highly resistive limit), we determine the precise location and shape of the coherent radio emission generation region within pulsar B's magnetosphere. We successfully reproduce orbital variations and secular evolution of the profile of B, as well as subpulse drift (due to reconnection between the magnetospheric and wind magnetic fields), and determine the location and the shape of the emission region. The emission region is located at about 3750 stellar radii and has a horseshoe-like shape, which is centred on the polar magnetic field lines. The best-fitting angular parameters of the emission region indicate that radio emission is generated on the field lines which, according to the theoretical models, originate close to the poles and carry the maximum current. We resolved all but one degeneracy in pulsar B's geometry. When considered together, the results of the two models converge and can explain why the modulation of B's radio emission at A's period is observed only within a certain orbital phase region. Our results imply that the wind of pulsar A has a striped structure only 1000 light-cylinder radii away. We discuss the implications of these results for pulsar magnetospheric models, mechanisms of coherent radio emission generation and reconnection rates in relativistic plasma.

Giant pulses of pulsar radio emission

OpenAIRE

Kuzmin, A. D.

2007-01-01

Review report of giant pulses of pulsar radio emission, based on our detections of four new pulsars with giant pulses, and the comparative analysis of the previously known pulsars with giant pulses, including the Crab pulsar and millisecond pulsar PSR B1937+21.

Radio-continuum emission from quasar host galaxies

International Nuclear Information System (INIS)

Condon, J. J.; Gower, A. C.; Hutchings, J. B.; Victoria Univ., Canada; Dominion Astrophysical Observatory, Victoria)

1987-01-01

Seven low-redshift quasars that are likely to be in spiral galaxies have been observed in a search for radio-continuum emission from the host galaxies of quasars. The properties of the individual quasars are listed, and 1.49 GHz contour maps of the seven quasar fields are presented. Map parameters and radio source parameters are given along with optical images of three of the objects. The results indicate that these quasars probably do reside in spiral galaxies. The radio luminosities, sizes, orientations, and u values all indicate that relativistic beaming alone cannot be used to explain the differences between the present sources and the far stronger radio sources seen in blazars or larger optically selected quasar samples. However, an apparent correlation between the radio luminosity and the ratio of the optical nuclear to host-galaxy luminosity is consistent with some beaming of nuclear radiation. 26 references

MULTIWAVELENGTH OBSERVATIONS OF RADIO-QUIET QUASARS WITH WEAK EMISSION LINES

International Nuclear Information System (INIS)

Plotkin, Richard M.; Anderson, Scott F.; MacLeod, Chelsea L.; Brandt, W. N.; Schneider, Donald P.; Diamond-Stanic, Aleksandar M.; Fan Xiaohui; Shemmer, Ohad

2010-01-01

We present radio and X-ray observations, as well as optical light curves, for a subset of 26 BL Lac candidates from the Sloan Digital Sky Survey (SDSS) lacking strong radio emission and with z < 2.2. Half of these 26 objects are shown to be stars, galaxies, or absorbed quasars. We conclude that the other 13 objects are active galactic nuclei (AGNs) with abnormally weak emission features; 10 of those 13 are definitively radio quiet, and, for those with available optical light curves, their level of optical flux variability is consistent with radio-quiet quasars. We cannot exclude the possibility that some of these 13 AGNs lie on the extremely radio-faint tail of the BL Lac distribution, but our study generally supports the notion that all BL Lac objects are radio-loud. These radio-quiet AGNs appear to have intrinsically weak or absent broad emission line regions (BELRs), and, based on their X-ray properties, we argue that some are low-redshift analogs to weak line quasars (WLQs). SDSS BL Lac searches are so far the only systematic surveys of the SDSS database capable of recovering such exotic low-redshift WLQs. There are 71 more z < 2.2 radio-quiet BL Lac candidates already identified in the SDSS, but not considered here, and many of those might be best unified with WLQs as well. Future studies combining low- and high-redshift WLQ samples will yield new insight on our understanding of the structure and formation of AGN BELRs.

A giant radio flare from Cygnus X-3 with associated γ-ray emission

Science.gov (United States)

Corbel, S.; Dubus, G.; Tomsick, J. A.; Szostek, A.; Corbet, R. H. D.; Miller-Jones, J. C. A.; Richards, J. L.; Pooley, G.; Trushkin, S.; Dubois, R.; Hill, A. B.; Kerr, M.; Max-Moerbeck, W.; Readhead, A. C. S.; Bodaghee, A.; Tudose, V.; Parent, D.; Wilms, J.; Pottschmidt, K.

2012-04-01

With frequent flaring activity of its relativistic jets, Cygnus X-3 (Cyg X-3) is one of the most active microquasars and is the only Galactic black hole candidate with confirmed high-energy γ-ray emission, thanks to detections by Fermi Large Area Telescope (Fermi/LAT) and AGILE. In 2011, Cyg X-3 was observed to transit to a soft X-ray state, which is known to be associated with high-energy γ-ray emission. We present the results of a multiwavelength campaign covering a quenched state, when radio emission from Cyg X-3 is at its weakest and the X-ray spectrum is very soft. A giant (˜20 Jy) optically thin radio flare marks the end of the quenched state, accompanied by rising non-thermal hard X-rays. Fermi/LAT observations (E≥ 100 MeV) reveal renewed γ-ray activity associated with this giant radio flare, suggesting a common origin for all non-thermal components. In addition, current observations unambiguously show that the γ-ray emission is not exclusively related to the rare giant radio flares. A three-week period of γ-ray emission is also detected when Cyg X-3 was weakly flaring in radio, right before transition to the radio quenched state. No γ-rays are observed during the ˜1-month long quenched state, when the radio flux is weakest. Our results suggest transitions into and out of the ultrasoft X-ray (radio-quenched) state trigger γ-ray emission, implying a connection to the accretion process, and also that the γ-ray activity is related to the level of radio flux (and possibly shock formation), strengthening the connection to the relativistic jets.

Fast Radio Bursts with Extended Gamma-Ray Emission?

International Nuclear Information System (INIS)

Murase, Kohta; Mészáros, Peter; Fox, Derek B.

2017-01-01

We consider some general implications of bright γ -ray counterparts to fast radio bursts (FRBs). We show that even if these manifest in only a fraction of FRBs, γ -ray detections with current satellites (including Swift ) can provide stringent constraints on cosmological FRB models. If the energy is drawn from the magnetic energy of a compact object such as a magnetized neutron star, the sources should be nearby and be very rare. If the intergalactic medium is responsible for the observed dispersion measure, the required γ -ray energy is comparable to that of the early afterglow or extended emission of short γ -ray bursts. While this can be reconciled with the rotation energy of compact objects, as expected in many merger scenarios, the prompt outflow that yields the γ -rays is too dense for radio waves to escape. Highly relativistic winds launched in a precursor phase, and forming a wind bubble, may avoid the scattering and absorption limits and could yield FRB emission. Largely independent of source models, we show that detectable radio afterglow emission from γ -ray bright FRBs can reasonably be anticipated. Gravitational wave searches can also be expected to provide useful tests.

The Detectability of Radio Auroral Emission from Proxima b

Energy Technology Data Exchange (ETDEWEB)

Burkhart, Blakesley; Loeb, Abraham [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA (United States)

2017-11-01

Magnetically active stars possess stellar winds whose interactions with planetary magnetic fields produce radio auroral emission. We examine the detectability of radio auroral emission from Proxima b, the closest known exosolar planet orbiting our nearest neighboring star, Proxima Centauri. Using the radiometric Bode’s law, we estimate the radio flux produced by the interaction of Proxima Centauri’s stellar wind and Proxima b’s magnetosphere for different planetary magnetic field strengths. For plausible planetary masses, Proxima b could produce radio fluxes of 100 mJy or more in a frequency range of 0.02–3 MHz for planetary magnetic field strengths of 0.007–1 G. According to recent MHD models that vary the orbital parameters of the system, this emission is expected to be highly variable. This variability is due to large fluctuations in the size of Proxima b’s magnetosphere as it crosses the equatorial streamer regions of dense stellar wind and high dynamic pressure. Using the MHD model of Garraffo et al. for the variation of the magnetosphere radius during the orbit, we estimate that the observed radio flux can vary nearly by an order of magnitude over the 11.2-day period of Proxima b. The detailed amplitude variation depends on the stellar wind, orbital, and planetary magnetic field parameters. We discuss observing strategies for proposed future space-based observatories to reach frequencies below the ionospheric cutoff (∼10 MHz), which would be required to detect the signal we investigate.

Virtual observatory tools and amateur radio observations supporting scientific analysis of Jupiter radio emissions

Science.gov (United States)

Cecconi, Baptiste; Hess, Sebastien; Le Sidaner, Pierre; Savalle, Renaud; Stéphane, Erard; Coffre, Andrée; Thétas, Emmanuel; André, Nicolas; Génot, Vincent; Thieman, Jim; Typinski, Dave; Sky, Jim; Higgins, Chuck; Imai, Masafumi

2016-04-01

In the frame of the preparation of the NASA/JUNO and ESA/JUICE (Jupiter Icy Moon Explorer) missions, and the development of a planetary sciences virtual observatory (VO), we are proposing a new set of tools directed to data providers as well as users, in order to ease data sharing and discovery. We will focus on ground based planetary radio observations (thus mainly Jupiter radio emissions), trying for instance to enhance the temporal coverage of jovian decametric emission. The data service we will be using is EPN-TAP, a planetary science data access protocol developed by Europlanet-VESPA (Virtual European Solar and Planetary Access). This protocol is derived from IVOA (International Virtual Observatory Alliance) standards. The Jupiter Routine Observations from the Nancay Decameter Array are already shared on the planetary science VO using this protocol, as well as data from the Iitate Low Frquency Radio Antenna, in Japan. Amateur radio data from the RadioJOVE project is also available. The attached figure shows data from those three providers. We will first introduce the VO tools and concepts of interest for the planetary radioastronomy community. We will then present the various data formats now used for such data services, as well as their associated metadata. We will finally show various prototypical tools that make use of this shared datasets.

Annals of the International Geophysical Year solar radio emission during the International Geophysical Year

CERN Document Server

Smerd, S F

1969-01-01

Annals of the International Geophysical Year, Volume 34: Solar Radio Emission During the International Geophysical Year covers the significant solar radio emission events observed during the International Geophysical Year (IGY). This book is composed of six chapters, and begins with a summary of tabulated quantities describing solar radio emission during the IGY. The tabulated figures illustrate the method of recording the position of radio sources on the sun, the use of symbols in describing the structure of bursts observed at single frequencies, and the different types used in a spectral

MAGNETIC FIELD STRUCTURE OF THE LARGE MAGELLANIC CLOUD FROM FARADAY ROTATION MEASURES OF DIFFUSE POLARIZED EMISSION

Energy Technology Data Exchange (ETDEWEB)

Mao, S. A. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); McClure-Griffiths, N. M.; McConnell, D. [Australia Telescope National Facility, CSIRO Astronomy and Space Science, Epping, NSW 1710 (Australia); Gaensler, B. M. [Sydney Institute for Astronomy, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia); Haverkorn, M. [Department of Astrophysics, Radboud University, P.O. Box 9010, 6500-GL Nijmegen (Netherlands); Beck, R. [Max-Planck-Institut fuer Radioastronomie, D-53121 Bonn (Germany); Wolleben, M. [Square Kilometre Array South Africa, The Park, Pinelands 7405 (South Africa); Stanimirovic, S. [Department of Astronomy, University of Wisconsin, Madison, WI 53706 (United States); Dickey, J. M. [Physics Department, University of Tasmania, Hobart, TAS 7001 (Australia); Staveley-Smith, L., E-mail: mao@astro.wisc.edu [International Centre for Radio Astronomy Research (ICRAR), The University of Western Australia, Crawley, WA 6009 (Australia)

2012-11-01

We present a study of the magnetic field of the Large Magellanic Cloud (LMC), carried out using diffuse polarized synchrotron emission data at 1.4 GHz acquired at the Parkes Radio Telescope and the Australia Telescope Compact Array. The observed diffuse polarized emission is likely to originate above the LMC disk on the near side of the galaxy. Consistent negative rotation measures (RMs) derived from the diffuse emission indicate that the line-of-sight magnetic field in the LMC's near-side halo is directed coherently away from us. In combination with RMs of extragalactic sources that lie behind the galaxy, we show that the LMC's large-scale magnetic field is likely to be of quadrupolar geometry, consistent with the prediction of dynamo theory. On smaller scales, we identify two brightly polarized filaments southeast of the LMC, associated with neutral hydrogen arms. The filaments' magnetic field potentially aligns with the direction toward the Small Magellanic Cloud (SMC). We suggest that tidal interactions between the SMC and the LMC in the past 10{sup 9} years are likely to have shaped the magnetic field in these filaments.

Magnetar-like X-Ray Bursts Suppress Pulsar Radio Emission

Energy Technology Data Exchange (ETDEWEB)

Archibald, R. F.; Lyutikov, M.; Kaspi, V. M.; Tendulkar, S. P. [Department of Physics and McGill Space Institute, McGill University, 3600 University Street, Montreal, QC H3A 2T8 (Canada); Burgay, M.; Possenti, A. [INAF–Osservatorio Astronomico di Cagliari, Via della Scienza 5, I-09047 Selargius (Italy); Esposito, P.; Rea, N. [Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands); Israel, G. [INAF–Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio Catone, Roma (Italy); Kerr, M. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Sarkissian, J. [CSIRO Astronomy and Space Science, Parkes Observatory, P.O. Box 276, Parkes, NSW 2870 (Australia); Scholz, P., E-mail: archibald@astro.utoronto.ca [National Research Council of Canada, Herzberg Astronomy and Astrophysics, Dominion Radio Astrophysical Observatory, P.O. Box 248, Penticton, BC V2A 6J9 (Canada)

2017-11-10

Rotation-powered pulsars and magnetars are two different observational manifestations of neutron stars: rotation-powered pulsars are rapidly spinning objects that are mostly observed as pulsating radio sources, while magnetars, neutron stars with the highest known magnetic fields, often emit short-duration X-ray bursts. Here, we report simultaneous observations of the high-magnetic-field radio pulsar PSR J1119−6127 at X-ray, with XMM-Newton and NuSTAR , and at radio energies with the Parkes radio telescope, during a period of magnetar-like bursts. The rotationally powered radio emission shuts off coincident with the occurrence of multiple X-ray bursts and recovers on a timescale of ∼70 s. These observations of related radio and X-ray phenomena further solidify the connection between radio pulsars and magnetars and suggest that the pair plasma produced in bursts can disrupt the acceleration mechanism of radio-emitting particles.

Scientists Detect Radio Emission from Rapidly Rotating Cosmic Dust Grains

Science.gov (United States)

2001-11-01

Astronomers have made the first tentative observations of a long-speculated, but never before detected, source of natural radio waves in interstellar space. Data from the National Science Foundation's 140 Foot Radio Telescope at the National Radio Astronomy Observatory in Green Bank, W.Va., show the faint, tell-tale signals of what appear to be dust grains spinning billions of times each second. This discovery eventually could yield a powerful new tool for understanding the interstellar medium - the immense clouds of gas and dust that populate interstellar space. The NRAO 140 Foot Radio Telescope The NRAO 140-Foot Radio Telescope "What we believe we have found," said Douglas P. Finkbeiner of Princeton University's Department of Astrophysics, "is the first hard evidence for electric dipole emission from rapidly rotating dust grains. If our studies are confirmed, it will be the first new source of continuum emission to be conclusively identified in the interstellar medium in nearly the past 20 years." Finkbeiner believes that these emissions have the potential in the future of revealing new and exciting information about the interstellar medium; they also may help to refine future studies of the Cosmic Microwave Background Radiation. The results from this study, which took place in spring 1999, were accepted for publication in Astrophysical Journal. Other contributors to this paper include David J. Schlegel, department of astrophysics, Princeton University; Curtis Frank, department of astronomy, University of Maryland; and Carl Heiles, department of astronomy, University of California at Berkeley. "The idea of dust grains emitting radiation by rotating is not new," comments Finkbeiner, "but to date it has been somewhat speculative." Scientists first proposed in 1957 that dust grains could emit radio signals, if they were caused to rotate rapidly enough. It was believed, however, that these radio emissions would be negligibly small - too weak to be of any impact to

Collective radio-emission from plasmas

International Nuclear Information System (INIS)

Papadopoulos, K.; Freund, H.P.

1979-01-01

Collective radiation processes operating in laboratory and space plasmas are reviewed with an emphasis towards astrophysical applications. Particular stress is placed on the physics involved in the various processes rather than in the detailed derivation of the formulas. Radiation processes from stable non-thermal, weakly turbulent and strongly turbulent magnetized and unmagnetized plasmas are discussed. The general theoretical ideas involved in amplification processes such as stimulated scattering are presented along with their application to free electron and plasma lasers. Direct radio-emission of electromagnetic waves by linear instabilities driven by beams or velocity anisotropies are shown to be of relevance in space applications. Finally, as an example of the computational state of the art pertaining to plasma radiation, a study of the type III solar radio bursts is presented. (orig.)

Radio emission from Supernovae and High Precision Astrometry

Science.gov (United States)

Perez-Torres, M. A.

1999-11-01

The present thesis work makes contributions in two scientific fronts: differential astrometry over the largest angular scales ever attempted (approx. 15 arcdegrees) and numerical simulations of radio emission from very young supernovae. In the first part, we describe the results of the use of very-long-baseline interferometry (VLBI) in one experiment designed to measure with very high precision the angular distance between the radio sources 1150+812 (QSO) and 1803+784 (BL Lac). We observed the radio sources on 19 November 1993 using an intercontinental array of radio telescopes, which simultaneously recorded at 2.3 and 8.4 GHz. VLBI differential astrometry is capable, Nature allowing, of yielding source positions with precisions well below the milliarcsecond level. To achieve this precision, we first had to accurately model the rotation of the interferometric fringes via the most precise models of Earth Orientation Parameters (EOP; precession, polar motion and UT1, nutation). With this model, we successfully connected our phase delay data at both frequencies and, using difference astrometric techniques, determined the coordinates of 1803+784 relative to those of 1150+812-within the IERS reference frame--with an standard error of about 0.6 mas in each coordinate. We then corrected for several effects including propagation medium (mainly the atmosphere and ionosphere), and opacity and source-structure effects within the radio sources. We stress that our dual-frequency measurements allowed us to accurately subtract the ionosphere contribution from our data. We also used GPS-based TEC measurements to independently find the ionosphere contribution, and showed that these contributions agree with our dual-frequency measurements within about 2 standard deviations in the less favorables cases (the longest baselines), but are usually well within one standard deviation. Our estimates of the relative positions, whether using dual-frequency-based or GPS-based ionosphere

Emissivity of discretized diffusion problems

International Nuclear Information System (INIS)

Densmore, Jeffery D.; Davidson, Gregory; Carrington, David B.

2006-01-01

The numerical modeling of radiative transfer by the diffusion approximation can produce artificially damped radiation propagation if spatial cells are too optically thick. In this paper, we investigate this nonphysical behavior at external problem boundaries by examining the emissivity of the discretized diffusion approximation. We demonstrate that the standard cell-centered discretization produces an emissivity that is too low for optically thick cells, a situation that leads to the lack of radiation propagation. We then present a modified boundary condition that yields an accurate emissivity regardless of cell size. This modified boundary condition can be used with a deterministic calculation or as part of a hybrid transport-diffusion method for increasing the efficiency of Monte Carlo simulations. We also discuss the range of applicability, as a function of cell size and material properties, when this modified boundary condition is employed in a hybrid technique. With a set of numerical calculations, we demonstrate the accuracy and usefulness of this modified boundary condition

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

International Nuclear Information System (INIS)

Weiler, Kurt W.; Panagia, Nino; Stockdale, Christopher; Rupen, Michael; Sramek, Richard A.; Williams, Christopher L.

2011-01-01

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.

A young source of optical emission from distant radio galaxies.

Science.gov (United States)

Hammer, F; Fèvre, O Le; Angonin, M C

1993-03-25

DISTANT radio galaxies provide valuable insights into the properties of the young Universe-they are the only known extended optical sources at high redshift and might represent an early stage in the formation and evolution of galaxies in general. This extended optical emission often has very complex morphologies, but the origin of the light is still unclear. Here we report spectroscopic observations for several distant radio galaxies (0.75≤ z ≤ 1.1) in which the rest-frame spectra exhibit featureless continua between 2,500 Å and 5,000 Å. We see no evidence for the break in the spectrum at 4,000 Å expected for an old stellar population 1-3 , and suggest that young stars or scattered emissions from the active nuclei are responsible for most of the observed light. In either case, this implies that the source of the optical emission is com-parable in age to the associated radio source, namely 10 7 years or less.

NONLINEAR WAVE INTERACTIONS AS EMISSION PROCESS OF TYPE II RADIO BURSTS

Energy Technology Data Exchange (ETDEWEB)

Ganse, Urs; Kilian, Patrick; Spanier, Felix [Lehrstuhl fuer Astronomie, Universitaet Wuerzburg, Wuerzburg (Germany); Vainio, Rami, E-mail: uganse@astro.uni-wuerzburg.de [Department of Physics, University of Helsinki, Helsinki (Finland)

2012-06-01

The emission of fundamental and harmonic frequency radio waves of type II radio bursts are assumed to be products of three-wave interaction processes of beam-excited Langmuir waves. Using a particle-in-cell code, we have performed simulations of the assumed emission region, a coronal mass ejection foreshock with two counterstreaming electron beams. Analysis of wavemodes within the simulation shows self-consistent excitation of beam-driven modes, which yield interaction products at both fundamental and harmonic emission frequencies. Through variation of the beam strength, we have investigated the dependence of energy transfer into electrostatic and electromagnetic modes, confirming the quadratic dependence of electromagnetic emission on electron beam strength.

NONLINEAR WAVE INTERACTIONS AS EMISSION PROCESS OF TYPE II RADIO BURSTS

International Nuclear Information System (INIS)

Ganse, Urs; Kilian, Patrick; Spanier, Felix; Vainio, Rami

2012-01-01

The emission of fundamental and harmonic frequency radio waves of type II radio bursts are assumed to be products of three-wave interaction processes of beam-excited Langmuir waves. Using a particle-in-cell code, we have performed simulations of the assumed emission region, a coronal mass ejection foreshock with two counterstreaming electron beams. Analysis of wavemodes within the simulation shows self-consistent excitation of beam-driven modes, which yield interaction products at both fundamental and harmonic emission frequencies. Through variation of the beam strength, we have investigated the dependence of energy transfer into electrostatic and electromagnetic modes, confirming the quadratic dependence of electromagnetic emission on electron beam strength.

Thermal radio emission from the winds of single stars

International Nuclear Information System (INIS)

Abbott, D.C.

1985-01-01

Observations of thermal emission at radio wavelengths provides a powerful diagnostic of the rate of mass loss and temperature of the winds of early-type stars. Some winds are also strong sources of nonthermal emission. Case studies of known thermal and nonthermal sources provide empirical criteria for classifying the observed radio radiation. Mass loss rates are derived for 37 OB and Wolf-Rayet stars considered definite or probable thermal wind sources by these criteria. The rate of mass loss is strongly linked to stellar luminosity in OB stars and probably linked to stellar mass in Wolf-Rayet stars, with no measurable correlation with any other stellar property. A few late-type giants and supergiants also have detectable thermal emission, which arises from extended, accelerating, partially-ionized chromospheres. (orig.)

The evening diffuse radio aurora, field-aligned currents and particle precipitation

International Nuclear Information System (INIS)

Unwin, R.S.

1980-01-01

The relationship of the afternoon/evening diffuse radio aurora, proton and electron precipitation and field-aligned currents is studied with data from the auroral radar at Slope Point, New Zealand, and the ISIS 2 satellite. It is shown that there is a very close association between the radio aurora and (primarily downward) field-aligned currents, which confirms and extends previous work, but that there is no clear relation with either proton or electron precipitation. (author)

Discovery of radio emission from the symbiotic X-ray binary system GX 1+4

Science.gov (United States)

van den Eijnden, J.; Degenaar, N.; Russell, T. D.; Miller-Jones, J. C. A.; Wijnands, R.; Miller, J. M.; King, A. L.; Rupen, M. P.

2018-02-01

We report the discovery of radio emission from the accreting X-ray pulsar and symbiotic X-ray binary GX 1+4 with the Karl G. Jansky Very Large Array. This is the first radio detection of such a system, wherein a strongly magnetized neutron star accretes from the stellar wind of an M-type giant companion. We measure a 9 GHz radio flux density of 105.3 ± 7.3 μJy, but cannot place meaningful constraints on the spectral index due to a limited frequency range. We consider several emission mechanisms that could be responsible for the observed radio source. We conclude that the observed properties are consistent with shocks in the interaction of the accretion flow with the magnetosphere, a synchrotron-emitting jet, or a propeller-driven outflow. The stellar wind from the companion is unlikely to be the origin of the radio emission. If the detected radio emission originates from a jet, it would show that strong magnetic fields (≥1012 G) do not necessarily suppress jet formation.

Radio emission from symbiotic stars: a binary model

International Nuclear Information System (INIS)

Taylor, A.R.; Seaquist, E.R.

1985-01-01

The authors examine a binary model for symbiotic stars to account for their radio properties. The system is comprised of a cool, mass-losing star and a hot companion. Radio emission arises in the portion of the stellar wind photo-ionized by the hot star. Computer simulations for the case of uniform mass loss at constant velocity show that when less than half the wind is ionized, optically thick spectral indices greater than +0.6 are produced. Model fits to radio spectra allow the binary separation, wind density and ionizing photon luminosity to be calculated. They apply the model to the symbiotic star H1-36. (orig.)

Dynamical evolution in clusters of galaxies with low-frequency radio emission

International Nuclear Information System (INIS)

Guthrie, B.N.G.

1977-01-01

Clusters of galaxies in which radio emission at low frequencies ( approximately 10 9 yr). Confinement would probably occur for radio sources associated with bright galaxies in the cores of clusters and cD galaxies in clusters. However, cD galaxies may have recurrent radio outbursts so that steep spectra are not always observed. (Auth.)

A giant radio flare from Cygnus X-3 with associated γ-ray emission: The 2011 radio and γ-ray flare of Cyg X-3

International Nuclear Information System (INIS)

Corbel, S.; Dubus, G.; Tomsick, J. A.; Szostek, A.

2012-01-01

With frequent flaring activity of its relativistic jets, Cygnus X-3 (Cyg X-3) is one of the most active microquasars and is the only Galactic black hole candidate with confirmed high-energy γ-ray emission, thanks to detections by Fermi Large Area Telescope (Fermi/LAT) and AGILE. In 2011, we observed Cyg X-3 in order to transit to a soft X-ray state, which is known to be associated with high-energy γ-ray emission. We present the results of a multiwavelength campaign covering a quenched state, when radio emission from Cyg X-3 is at its weakest and the X-ray spectrum is very soft. A giant (~20 Jy) optically thin radio flare marks the end of the quenched state, accompanied by rising non-thermal hard X-rays. Fermi/LAT observations (E≥ 100 MeV) reveal renewed γ-ray activity associated with this giant radio flare, suggesting a common origin for all non-thermal components. In addition, current observations unambiguously show that the γ-ray emission is not exclusively related to the rare giant radio flares. A three-week period of γ-ray emission is also detected when Cyg X-3 was weakly flaring in radio, right before transition to the radio quenched state. There were no γ-rays observed during the ~1-month long quenched state, when the radio flux is weakest. These results suggest transitions into and out of the ultrasoft X-ray (radio-quenched) state trigger γ-ray emission, implying a connection to the accretion process, and also that the γ-ray activity is related to the level of radio flux (and possibly shock formation), strengthening the connection to the relativistic jets.

The Correlation between γ-Ray and Radio Emissions for the Fermi ...

Indian Academy of Sciences (India)

Abstract. Based upon the Fermi blazars sample, the radio and γ-ray emissions are compiled for a sample of 74 γ-ray loud blazars to calculate the radio to γ-ray effective spectrum index αRγ . The correlations between. αRγ and γ-ray luminosity, and between radio and γ-ray luminosity are also investigated. Key words.

A Link Between X-ray Emission Lines and Radio Jets in 4U 1630-47?

Science.gov (United States)

Neilsen, Joseph; Coriat, Mickaël; Fender, Rob; Lee, Julia C.; Ponti, Gabriele; Tzioumis, A.; Edwards, Phillip; Broderick, Jess

2014-06-01

Recently, Díaz Trigo et al. reported an XMM-Newton detection of relativistically Doppler-shifted emission lines associated with steep-spectrum radio emission in the stellar-mass black hole candidate 4U 1630-47 during its 2012 outburst. They interpreted these lines as indicative of a baryonic jet launched by the accretion disk. We present a search for the same lines earlier in the same outburst using high-resolution X-ray spectra from the Chandra HETGS. While our observations (eight months prior to the XMM-Newton campaign) also coincide with detections of steep spectrum radio emission by the Australia Telescope Compact Array, we find a strong disk wind but no evidence for any relativistic X-ray emission lines. Indeed, despite ˜5× brighter radio emission, our Chandra spectra allow us to place an upper limit on the flux in the blueshifted Fe XXVI line that is ˜20× weaker than the line observed by Díaz Trigo et al. Thus we can conclusively say that radio emission is not universally associated with relativistically Doppler-shifted emission lines in 4U 1630-47. We explore several scenarios that could explain our differing results, including variations in the geometry of the jet or a mass-loading process or jet baryon content that evolves with the accretion state of the black hole. We also consider the possibility that the radio emission arises in an interaction between a jet and the nearby ISM, in which case the X-ray emission lines might be unrelated to the radio emission.

Radio continuum emission from winds, chromospheres, and coronae of cool giants and supergiants

International Nuclear Information System (INIS)

Drake, S.A.; Linsky, J.L.

1986-01-01

In this paper we present the results of a sensitive VLA radio continuum survey at 6 cm of 39 of the nearest, single cool giants and supergiants with spectral types in the range G0--M5. We discuss our findings in the context of the various mechanisms that might be producing radio emission in these cool stars. We have definitely detected four K and M giants (α 1 Her, α Boo, rho Per, and μ Gem) and probably detected a fifth ( β UMi) at flux levels of 0.1--1.0 mJy. We believe that in all five of these cases the radio emission is thermal emission from cool stellar winds. We have made additional 2 cm observations of several stars, including the four stars definitely detected at 6 cm. We have derived spectral indices for α Boo, α 1 Her, and rho Per of 0.80, 0.84, and 0.95, respectively, that are close to the 0.6 value predicted by standard stellar wind models in the optically thick regime. An additional cool giant (α Tau) was detected only at 2 cm, implying a spectral index of > or =0.87. None of the coronal or hybrid-chromosphere giants observed were detected in this study, with the exception of α Aur, a 0.2 mJy radio source at 6 cm, which is in fact a widely separated, long-period (P/sub orb/approx.104/sup d/) RS CVn system containing two cool giant stars. In this case, we believe that the 6 cm radio emission is optically thin, thermal emission from the corona(e) of one or both of the components, since the radio-emission measure is consistent with that of the observed x-ray emission

Onion-shell model for cosmic ray electrons and radio synchrotron emission in supernova remnants

International Nuclear Information System (INIS)

Beck, R.; Drury, L.O.; Voelk, H.J.; Bogdan, T.J.

1985-01-01

The spectrum of cosmic ray electrons, accelerated in the shock front of a supernova remnant (SNR), is calculated in the test-particle approximation using an onion-shell model. Particle diffusion within the evolving remnant is explicity taken into account. The particle spectrum becomes steeper with increasing radius as well as SNR age. Simple models of the magnetic field distribution allow a prediction of the intensity and spectrum of radio synchrotron emission and their radial variation. The agreement with existing observations is satisfactory in several SNR's but fails in other cases. Radiative cooling may be an important effect, especially in SNR's exploding in a dense interstellar medium

Onion-shell model for cosmic ray electrons and radio synchrotron emission in supernova remnants

Science.gov (United States)

Beck, R.; Drury, L. O.; Voelk, H. J.; Bogdan, T. J.

1985-01-01

The spectrum of cosmic ray electrons, accelerated in the shock front of a supernova remnant (SNR), is calculated in the test-particle approximation using an onion-shell model. Particle diffusion within the evolving remnant is explicity taken into account. The particle spectrum becomes steeper with increasing radius as well as SNR age. Simple models of the magnetic field distribution allow a prediction of the intensity and spectrum of radio synchrotron emission and their radial variation. The agreement with existing observations is satisfactory in several SNR's but fails in other cases. Radiative cooling may be an important effect, especially in SNR's exploding in a dense interstellar medium.

TeV Diffuse Emission From the Inner Galaxy

Directory of Open Access Journals (Sweden)

Amid Nayerhoda

2018-04-01

Full Text Available The TeV diffuse emission from the Galactic plane is produced by multi TeV electrons and nuclei interacting with radiation fields and ambient gas, respectively. Measurements of the TeV diffuse emission help constrain CR origin and transport properties. We present a preliminary analysis of HAWC diffuse emission data from the inner Galaxy. The HAWC measurements will be used to constrain particle transport properties close to the Galaxy center correlating the HAWC maps with predictions of the DRAGON code.

Solar radio emissions: 2D full PIC simulations

Science.gov (United States)

Pierre, H.; Sgattoni, A.; Briand, C.; Amiranoff, F.; Riconda, C.

2016-12-01

Solar radio emissions are electromagnetic waves observed at the local plasma frequency and/or at twice the plasma frequency. To describe their origin a multi-stage model has been proposed by Ginzburg & Zhelezniakov (1958) and further developed by several authors, which consider a succession of non-linear three-wave interaction processes. Electron beams accelerated by solar flares travel in the interplanetary plasma and provide the free energy for the development of plasma instabilities. The model describes how part of the free energy of these beams can be transformed in a succession of plasma waves and eventually into electromagnetic waves. Following the work of Thurgood & Tsiklauri (2015) we performed several 2D Particle In Cell simulations. The simulations follow the entire set of processes from the electron beam propagation in the background plasma to the generation of the electromagnetic waves in particular the 2ωp emission, including the excitation of the low frequency waves. As suggested by Thurgood & Tsiklauri (2015) it is possible to identify regimes where the radiation emission can be directly linked to the electron beams. Our attention was devoted to estimate the conversion efficiency from electron kinetic energy to the em energy, and the growth rate of the several processes which can be identified. We studied the emission angles of the 2ωpradiation and compared them with the theoretical predictions of Willes et. al. (1995). We also show the role played by some numerical parameters i.e. the size and shape of the simulation box. This work is the first step to prepare laser-plasma experiments. V. L. Ginzburg, V. V. Zhelezniakov On the Possible Mechanisms of Sporadic Solar Radio Emission (Radiation in an Isotropic Plasma) Soviet Astronomy, Vol. 2, p.653 (1958) J. O. Thurgood and D. Tsiklauri Self-consistent particle-in-cell simulations of funda- mental and harmonic plasma radio emission mechanisms. Astronomy & Astrophysics 584, A83 (2015). A. Willes, P

Identification of radio emission from the Io flux tube

International Nuclear Information System (INIS)

Riddle, A.C.

1983-01-01

Many theories and observations suggest that Jovian decametric radio emission is generated in flux tubes that pass close to Io's orbit. However, comparison of theory and observation is hindered by lack of knowledge as to which specific flux tube is responsible for a particular emission. In this note, emission from the instantaneous Io flux tube is identified. This makes possible a mapping of emissions onto the causative flux tubes for a significant range of Jovian longitudes (240 0 --360 0 )

Radio ejection and broad forbidden emission lines in the Seyfert galaxy NGC 7674

International Nuclear Information System (INIS)

Unger, S.W.; Pedlar, A.; Axon, D.J.

1988-01-01

The Seyfert nucleus in NGC7674 (Mkn533) is remarkable for its broad asymmetric forbidden line profiles, which extend 2000 kms -1 blueward of the systemic velocity. The galaxy also has a compact nuclear radio source. We have obtained new high-resolution radio observations of NGC7674, using the European VLBI network and the VLA, and optical spectroscopic observations using the Isaac Newton Telescope. The radio maps reveal a triple radio source with a total angular extent of about 0.7 arcsec, and provide evidence that the radio emission is powered by collimated ejection. In the plane of the sky, the ejection axis appears roughly perpendicular to the galactic rotation axis. Although the dominant radio components are separated by 0.5 arcsec, the broad [OIII]λ5007 line emission is confined to within about 0.25 arcsec of the continuum nucleus. (author)

Wavelet Based Characterization of Low Radio Frequency Solar Emissions

Science.gov (United States)

Suresh, A.; Sharma, R.; Das, S. B.; Oberoi, D.; Pankratius, V.; Lonsdale, C.

2016-12-01

Low-frequency solar radio observations with the Murchison Widefield Array (MWA) have revealed the presence of numerous short-lived, narrow-band weak radio features, even during quiet solar conditions. In their appearance in in the frequency-time plane, they come closest to the solar type III bursts, but with much shorter spectral spans and flux densities, so much so that they are not detectable with the usual swept frequency radio spectrographs. These features occur at rates of many thousand features per hour in the 30.72 MHz MWA bandwidth, and hence necessarily require an automated approach to determine robust statistical estimates of their properties, e.g., distributions of spectral widths, temporal spans, flux densities, slopes in the time-frequency plane and distribution over frequency. To achieve this, a wavelet decomposition approach has been developed for feature recognition and subsequent parameter extraction from the MWA dynamic spectrum. This work builds on earlier work by the members of this team to achieve a reliable flux calibration in a computationally efficient manner. Preliminary results show that the distribution of spectral span of these features peaks around 3 MHz, most of them last for less than two seconds and are characterized by flux densities of about 60% of the background solar emission. In analogy with the solar type III bursts, this non-thermal emission is envisaged to arise via coherent emission processes. There is also an exciting possibility that these features might correspond to radio signatures of nanoflares, hypothesized (Gold, 1964; Parker, 1972) to explain coronal heating.

From Radio with Love: An Overview of the Role of Radio Observations in Understanding High-Energy Emission from Active Galaxies

Science.gov (United States)

Ojha, Roopesh

2012-01-01

The gamma-ray satellite Fermi and the ground based TeV facilities MAGIC, VERITAS and HESS have ushered in a new era in the observation of high-energy emission from active galaxies. The energy budgets of these objects have a major contribution from gamma-rays and it is simply not possible to understand their physics without high-energy observations. Though the exact mechanisms for high-energy production in galaxies remains an open question, gamma-rays typically result from interactions between high-energy particles. Via different interactions these same particles can produce radio emission. Thus the non-thermal nature of gamma-ray emission practically guarantees that high-energy emitters are also radio loud. Aside from their obvious role as a component of multiwavelength analysis, radio observations provide two crucial elements essential to understanding the source structure and physical processes of high-energy emitters: very high timing resolution and very high spatial resolution. A brief overview of the unique role played by radio observations in unraveling the mysteries of the high energy Universe as presented here.

Cosmic ray radio emission as air shower detection

International Nuclear Information System (INIS)

Curutiu, Alexandru; Rusu, Mircea; Isar, Gina; Zgura, Sorin

2004-01-01

The possibility of radio-detection of ultra-high energy cosmic rays (within the 10 to 100 MHz range) are discussed. Currently, air showers are detected by various methods, mainly based on particle detectors (KASCADE, Auger) or optical detection (Cerenkov radiation). Recently,to detect radio emission from cosmic ray air showers a method using electromagnetic radiation in low frequency domain (LOFAR) was proposed. We are investigating this possibility, using simulation codes created to investigate electromagnetic radiation of intricate antennae structure, for example fractal antennas. Some of the preliminary results will be communicated in this session. (authors)

Radio emission from the nova-like variable AC Cancri and the symbiotic variable AG Draconis

International Nuclear Information System (INIS)

Torbett, M.V.; Campbell, B.; Mount Wilson and Las Campanas Observatories, Pasadena, CA)

1987-01-01

Radio emission at 6 cm has been detected from the nova-like cataclysmic variable AC Cnc and the symbiotic variable AG Dra. The AC Cnc observation constitutes the first radio detection in this class of objects. The AG Dra source is probably resolved and appears to show asymmetric, extended structure. The radio emission can best be explained by thermal bremsstrahlung. 26 references

Radio jets and gamma-ray emission in radio-silent narrow-line Seyfert 1 galaxies

Science.gov (United States)

Lähteenmäki, A.; Järvelä, E.; Ramakrishnan, V.; Tornikoski, M.; Tammi, J.; Vera, R. J. C.; Chamani, W.

2018-06-01

We have detected six narrow-line Seyfert 1 (NLS1) galaxies at 37 GHz that were previously classified as radio silent and two that were classified as radio quiet. These detections reveal the presumption that NLS1 galaxies labelled radio quiet or radio silent and hosted by spiral galaxies are unable to launch jets to be incorrect. The detections are a plausible indicator of the presence of a powerful, most likely relativistic jet because this intensity of emission at 37 GHz cannot be explained by, for example, radiation from supernova remnants. Additionally, one of the detected NLS1 galaxies is a newly discovered source of gamma rays and three others are candidates for future detections. 37 GHz data are only available in electronic form at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/614/L1

RADIO EMISSION FROM RED-GIANT HOT JUPITERS

International Nuclear Information System (INIS)

Fujii, Yuka; Spiegel, David S.; Mroczkowski, Tony; Nordhaus, Jason; Zimmerman, Neil T.; Parsons, Aaron R.; Mirbabayi, Mehrdad; Madhusudhan, Nikku

2016-01-01

When planet-hosting stars evolve off the main sequence and go through the red-giant branch, the stars become orders of magnitudes more luminous and, at the same time, lose mass at much higher rates than their main-sequence counterparts. Accordingly, if planetary companions exist around these stars at orbital distances of a few au, they will be heated up to the level of canonical hot Jupiters and also be subjected to a dense stellar wind. Given that magnetized planets interacting with stellar winds emit radio waves, such “Red-Giant Hot Jupiters” (RGHJs) may also be candidate radio emitters. We estimate the spectral auroral radio intensity of RGHJs based on the empirical relation with the stellar wind as well as a proposed scaling for planetary magnetic fields. RGHJs might be intrinsically as bright as or brighter than canonical hot Jupiters and about 100 times brighter than equivalent objects around main-sequence stars. We examine the capabilities of low-frequency radio observatories to detect this emission and find that the signal from an RGHJ may be detectable at distances up to a few hundred parsecs with the Square Kilometer Array

RADIO EMISSION FROM RED-GIANT HOT JUPITERS

Energy Technology Data Exchange (ETDEWEB)

Fujii, Yuka [Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, 152-8550 (Japan); Spiegel, David S. [Analytics and Algorithms, Stitch Fix, San Francisco, CA 94103 (United States); Mroczkowski, Tony [Naval Research Laboratory, 4555 Overlook Ave SW, Washington, DC 20375 (United States); Nordhaus, Jason [Department of Science and Mathematics, National Technical Institute for the Deaf, Rochester Institute of Technology, Rochester, NY 14623 (United States); Zimmerman, Neil T. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Parsons, Aaron R. [Astronomy Department, University of California, Berkeley, CA (United States); Mirbabayi, Mehrdad [Astrophysics Department, Institute for Advanced Study, Princeton, NJ 08540 (United States); Madhusudhan, Nikku, E-mail: yuka.fujii@elsi.jp [Astronomy Department, University of Cambridge (United Kingdom)

2016-04-01

When planet-hosting stars evolve off the main sequence and go through the red-giant branch, the stars become orders of magnitudes more luminous and, at the same time, lose mass at much higher rates than their main-sequence counterparts. Accordingly, if planetary companions exist around these stars at orbital distances of a few au, they will be heated up to the level of canonical hot Jupiters and also be subjected to a dense stellar wind. Given that magnetized planets interacting with stellar winds emit radio waves, such “Red-Giant Hot Jupiters” (RGHJs) may also be candidate radio emitters. We estimate the spectral auroral radio intensity of RGHJs based on the empirical relation with the stellar wind as well as a proposed scaling for planetary magnetic fields. RGHJs might be intrinsically as bright as or brighter than canonical hot Jupiters and about 100 times brighter than equivalent objects around main-sequence stars. We examine the capabilities of low-frequency radio observatories to detect this emission and find that the signal from an RGHJ may be detectable at distances up to a few hundred parsecs with the Square Kilometer Array.

Radio Emission from Red-Giant Hot Jupiters

Science.gov (United States)

Fujii, Yuka; Spiegel, David S.; Mroczkowski, Tony; Nordhaus, Jason; Zimmerman, Neil T.; Parsons, Aaron R.; Mirbabayi, Mehrdad; Madhusudhan, Nikku

2016-01-01

When planet-hosting stars evolve off the main sequence and go through the red-giant branch, the stars become orders of magnitudes more luminous and, at the same time, lose mass at much higher rates than their main sequence counterparts. Accordingly, if planetary companions exist around these stars at orbital distances of a few au, they will be heated up to the level of canonical hot Jupiters and also be subjected to a dense stellar wind. Given that magnetized planets interacting with stellar winds emit radio waves, such "Red-Giant Hot Jupiters" (RGHJs) may also be candidate radio emitters. We estimate the spectral auroral radio intensity of RGHJs based on the empirical relation with the stellar wind as well as a proposed scaling for planetary magnetic fields. RGHJs might be intrinsically as bright as or brighter than canonical hot Jupiters and about 100 times brighter than equivalent objects around main-sequence stars. We examine the capabilities of low-frequency radio observatories to detect this emission and find that the signal from an RGHJ may be detectable at distances up to a few hundred parsecs with the Square Kilometer Array.

A LINK BETWEEN X-RAY EMISSION LINES AND RADIO JETS IN 4U 1630-47?

Energy Technology Data Exchange (ETDEWEB)

Neilsen, Joseph [Department of Astronomy, Boston University, Boston, MA 02215 (United States); Coriat, Mickaël [Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa); Fender, Rob; Broderick, Jess W. [Department of Physics, Oxford University, Oxford OX1 3RH (United Kingdom); Lee, Julia C. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Ponti, Gabriele [Max Planck Institute fur Extraterrestriche Physik, D-85748 Garching (Germany); Tzioumis, Anastasios K.; Edwards, Philip G., E-mail: neilsenj@bu.edu [CSIRO Astronomy and Space Science, Australia Telescope National Facility, P.O. Box 76, Epping, NSW 1710 (Australia)

2014-03-20

Recently, Díaz Trigo et al. reported an XMM-Newton detection of relativistically Doppler-shifted emission lines associated with steep-spectrum radio emission in the stellar-mass black hole candidate 4U 1630-47 during its 2012 outburst. They interpreted these lines as indicative of a baryonic jet launched by the accretion disk. Here we present a search for the same lines earlier in the same outburst using high-resolution X-ray spectra from the Chandra HETGS. While our observations (eight months prior to the XMM-Newton campaign) also coincide with detections of steep spectrum radio emission by the Australia Telescope Compact Array, we find no evidence for any relativistic X-ray emission lines. Indeed, despite ∼5 × brighter radio emission, our Chandra spectra allow us to place an upper limit on the flux in the blueshifted Fe XXVI line that is ≳ 20 × weaker than the line observed by Díaz Trigo et al. We explore several scenarios that could explain our differing results, including variations in the geometry of the jet or a mass-loading process or jet baryon content that evolves with the accretion state of the black hole. We also consider the possibility that the radio emission arises in an interaction between a jet and the nearby interstellar medium, in which case the X-ray emission lines might be unrelated to the radio emission.

A LINK BETWEEN X-RAY EMISSION LINES AND RADIO JETS IN 4U 1630-47?

International Nuclear Information System (INIS)

Neilsen, Joseph; Coriat, Mickaël; Fender, Rob; Broderick, Jess W.; Lee, Julia C.; Ponti, Gabriele; Tzioumis, Anastasios K.; Edwards, Philip G.

2014-01-01

Recently, Díaz Trigo et al. reported an XMM-Newton detection of relativistically Doppler-shifted emission lines associated with steep-spectrum radio emission in the stellar-mass black hole candidate 4U 1630-47 during its 2012 outburst. They interpreted these lines as indicative of a baryonic jet launched by the accretion disk. Here we present a search for the same lines earlier in the same outburst using high-resolution X-ray spectra from the Chandra HETGS. While our observations (eight months prior to the XMM-Newton campaign) also coincide with detections of steep spectrum radio emission by the Australia Telescope Compact Array, we find no evidence for any relativistic X-ray emission lines. Indeed, despite ∼5 × brighter radio emission, our Chandra spectra allow us to place an upper limit on the flux in the blueshifted Fe XXVI line that is ≳ 20 × weaker than the line observed by Díaz Trigo et al. We explore several scenarios that could explain our differing results, including variations in the geometry of the jet or a mass-loading process or jet baryon content that evolves with the accretion state of the black hole. We also consider the possibility that the radio emission arises in an interaction between a jet and the nearby interstellar medium, in which case the X-ray emission lines might be unrelated to the radio emission

The structure of the radio emission from the NGC 1579/LkHα101 region

International Nuclear Information System (INIS)

Brown, R.L.; Broderick, J.J.; Knapp, G.R.

1976-01-01

Radio-frequency observations at 3.7 and 11 cm of the NGC 1579/LkHα101 region show that the radio emission arises in a compact, < 1'' core concentric with a more extended approximately 1' emission region. At these wavelengths the compact component is optically thick, with a spectrum increasing as ν, whereas the extended region is optically thin and contributes at least 80 per cent of the total flux density. LkHα101 appears to be the source of excitation for all of the radio emission; this result, together with the total infrared luminosity, suggests that an appropriate spectral classification for LkHα101 is B1 IIe. (author)

Radio continuum emission from young stellar objects in L1641

International Nuclear Information System (INIS)

Morgan, J.A.; Snell, R.L.; Strom, K.M.

1990-01-01

The results of a 6 and 20 cm radio continuum survey of young stellar objects in the L1641 region located south of the Orion Nebula are presented. Four are identified as low-luminosity young stellar objects in L1641 and three more as Herbig-Haro or Herbig-Haro-like objects. These objects have bolometric luminosities between 80 and 300 solar, and their 6-20 cm spectral index suggests optically thick, free-free emission. They are characterized by a rising spectrum between 2.2 and 25 microns, have no optical counterparts, and are associated with stellar wind activity. Thus, detectable radio continuum emission may be produced only by the youngest and most luminous objects in L1641. 34 refs

Blazars with arcminute-scale radio halos

International Nuclear Information System (INIS)

Ulvestad, J.S.; Antonucci, R.R.J.; Space Telescope Science Institute, Baltimore, MD)

1986-01-01

About 10-arcsec resolution 20-cm wavelength maps are presented for three nearby BL Lac objects: Mkn 180, whose halo has a linear size of 85 kpc, 2155-304, with a halo about 375 kpc across, and 1727 + 502, whose one-sided diffuse emission extends to a distance of about 145 kpc from its radio core. Little evidence is found for strong radio variability in the cores of the three blazars; these and other results obtained are consistent with the assertion that the three objects should be classified as normal low luminosity double radio galaxies with optically dull nuclei, if seen from other directions. 20 references

X-ray Emission from the Radio Jet in 3C 120

DEFF Research Database (Denmark)

Harris, D. E.; Hjorth, J.; Sadun, A. C.

1999-01-01

We report the discovery of X-ray emission from a radio knot at a projected distance of 25" from the nucleus of the Seyfert galaxy, 3C 120. The data were obtained with the ROSAT High Resolution Imager (HRI). Optical upper limits for the knot preclude a simple power law extension of the radio...

Infrared and radio emission from S0 galaxies

International Nuclear Information System (INIS)

Bally, J.; Thronson, H.A. Jr.

1989-01-01

Far-IR data are presented on 74 early-type S0 galaxies that were selected on the basis of the availability of radio-continuum measurements. Most of the galaxies are detected at IR wavelengths with IRAS, indicating the presence of a cold interstellar medium (ISM) in these galaxies. The mass of gas in these systems is estimated to lie in the range of 10 to the 7th to 10 to the 10th solar. The most massive ISM in some S0s approaches that found in some spirals. The brighter IR-emitting galaxies all lie close to a relationship established for gas-rich spiral galaxies. None of these galaxies have large ratio fluxes, suggesting that strong nuclear radio sources or extended radio lobes and jets are absent or suppressed. Strong radio emission is found among those galaxies that are either faint or not detected at IR wavelengths. The absence of an ISM suggests that these galaxies are of an earlier type that those that have large IR fluxes. 38 references

THE ABSENCE OF RADIO EMISSION FROM THE GLOBULAR CLUSTER G1

Energy Technology Data Exchange (ETDEWEB)

Miller-Jones, J. C. A. [International Centre for Radio Astronomy Research, Curtin University, GPO Box U1987, Perth, WA 6845 (Australia); Wrobel, J. M. [NRAO Domenici Science Operations Center, 1003 Lopezville Road, Socorro, NM 87801 (United States); Sivakoff, G. R.; Heinke, C. O.; Miller, R. E. [Department of Physics, University of Alberta, Room 238 CEB, Edmonton, AB T6G 2G7 (Canada); Plotkin, R. M. [Astronomical Institute ' Anton Pannekoek' , University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Di Stefano, R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Greene, J. E. [Department of Astronomy, University of Texas at Austin, 1 University Station C1400, Austin, TX 71712 (United States); Ho, L. C. [The Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Joseph, T. D.; Maccarone, T. J. [School of Physics and Astronomy, University of Southampton, Highfield SO17 IBJ (United Kingdom); Kong, A. K. H., E-mail: james.miller-jones@curtin.edu.au [Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

2012-08-10

The detections of both X-ray and radio emission from the cluster G1 in M31 have provided strong support for existing dynamical evidence for an intermediate-mass black hole (IMBH) of mass (1.8 {+-} 0.5) Multiplication-Sign 10{sup 4} M{sub Sun} at the cluster center. However, given the relatively low significance and astrometric accuracy of the radio detection, and the non-simultaneity of the X-ray and radio measurements, this identification required further confirmation. Here we present deep, high angular resolution, strictly simultaneous X-ray and radio observations of G1. While the X-ray emission (L{sub X} = 1.74{sup +0.53}{sub -0.44} Multiplication-Sign 10{sup 36} (d/750 kpc){sup 2} erg s{sup -1} in the 0.5-10 keV band) remained fully consistent with previous observations, we detected no radio emission from the cluster center down to a 3{sigma} upper limit of 4.7 {mu}Jy beam{sup -1}. Our favored explanation for the previous radio detection is flaring activity from a black hole low-mass X-ray binary (LMXB). We performed a new regression of the 'Fundamental Plane' of black hole activity, valid for determining black hole mass from radio and X-ray observations of sub-Eddington black holes, finding log M{sub BH} = (1.638 {+-} 0.070)log L{sub R} - (1.136 {+-} 0.077)log L{sub X} - (6.863 {+-} 0.790), with an empirically determined uncertainty of 0.44 dex. This constrains the mass of the X-ray source in G1, if a black hole, to be <9.7 Multiplication-Sign 10{sup 3} M{sub Sun} at 95% confidence, suggesting that it is a persistent LMXB. This annuls what was previously the most convincing evidence from radiation for an IMBH in the Local Group, though the evidence for an IMBH in G1 from velocity dispersion measurements remains unaffected by these results.

Sources of the Radio Background Considered

Energy Technology Data Exchange (ETDEWEB)

Singal, J.; /KIPAC, Menlo Park /Stanford U.; Stawarz, L.; /KIPAC, Menlo Park /Stanford U. /Jagiellonian U., Astron. Observ.; Lawrence, A.; /Edinburgh U., Inst. Astron. /KIPAC, Menlo Park /Stanford U.; Petrosian, V.; /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept.

2011-08-22

We investigate possible origins of the extragalactic radio background reported by the ARCADE 2 collaboration. The surface brightness of the background is several times higher than that which would result from currently observed radio sources. We consider contributions to the background from diffuse synchrotron emission from clusters and the intergalactic medium, previously unrecognized flux from low surface brightness regions of radio sources, and faint point sources below the flux limit of existing surveys. By examining radio source counts available in the literature, we conclude that most of the radio background is produced by radio point sources that dominate at sub {mu}Jy fluxes. We show that a truly diffuse background produced by elections far from galaxies is ruled out because such energetic electrons would overproduce the observed X-ray/{gamma}-ray background through inverse Compton scattering of the other photon fields. Unrecognized flux from low surface brightness regions of extended radio sources, or moderate flux sources missed entirely by radio source count surveys, cannot explain the bulk of the observed background, but may contribute as much as 10%. We consider both radio supernovae and radio quiet quasars as candidate sources for the background, and show that both fail to produce it at the observed level because of insufficient number of objects and total flux, although radio quiet quasars contribute at the level of at least a few percent. We conclude that the most important population for production of the background is likely ordinary starforming galaxies above redshift 1 characterized by an evolving radio far-infrared correlation, which increases toward the radio loud with redshift.

Dark matter in the Reticulum II dSph: a radio search

Science.gov (United States)

Regis, Marco; Richter, Laura; Colafrancesco, Sergio

2017-07-01

We present a deep radio search in the Reticulum II dwarf spheroidal (dSph) galaxy performed with the Australia Telescope Compact Array. Observations were conducted at 16 cm wavelength, with an rms sensitivity of 0.01 mJy/beam, and with the goal of searching for synchrotron emission induced by annihilation or decay of weakly interacting massive particles (WIMPs). Data were complemented with observations on large angular scales taken with the KAT-7 telescope. We find no evidence for a diffuse emission from the dSph and we derive competitive bounds on the WIMP properties. In addition, we detect more than 200 new background radio sources. Among them, we show there are two compelling candidates for being the radio counterpart of the possible γ-ray emission reported by other groups using Fermi-LAT data.

Dark matter in the Reticulum II dSph: a radio search

International Nuclear Information System (INIS)

Regis, Marco; Richter, Laura; Colafrancesco, Sergio

2017-01-01

We present a deep radio search in the Reticulum II dwarf spheroidal (dSph) galaxy performed with the Australia Telescope Compact Array. Observations were conducted at 16 cm wavelength, with an rms sensitivity of 0.01 mJy/beam, and with the goal of searching for synchrotron emission induced by annihilation or decay of weakly interacting massive particles (WIMPs). Data were complemented with observations on large angular scales taken with the KAT-7 telescope. We find no evidence for a diffuse emission from the dSph and we derive competitive bounds on the WIMP properties. In addition, we detect more than 200 new background radio sources. Among them, we show there are two compelling candidates for being the radio counterpart of the possible γ-ray emission reported by other groups using Fermi-LAT data.

Radio emission, cosmic ray electrons, and the production of γ-rays in the galaxy

International Nuclear Information System (INIS)

Webber, W.R.; Simpson, G.A.; Cane, H.V.

1980-01-01

Using a perspective based on new radio data, we have reexamined the traditional derivation of the interstellar electron spectrum using the galactic nonthermal radio spectrum. The radio spectrum derived in the polar directions is now used as a base for this derivation rather than the anticenter spectrum. The interstellar electron spectrum between 70 and 1200 MeV is found to have an exponent -2.14 +- 0.06, steeper than previously determined, and leading to electron fluxes at low energies up to a factor of 10 larger than previously predicted. The electron spectrum below approx.20 MeV measured at Earth is used along with solar modulation arguments to suggest that this interstellar electron spectrum flattens to an exponent of -1.6 +- 0.1 between 5 and 70 MeV. We then use radio maps to predict the γ-ray fluxes produced by the bremsstrahlung process to be expected from these electrons. Using the radio maps, we fiest define L/sub eff/, the effective path length for radio emission in various directions, to predict the effective path length for γ-ray emission. The spectral shapes of γ-rays predicted when the contribution from π 0 decay is included, show little evidence of a pion-decay bump and agree well with those observed, indicating that large changes in the cosmic-ray electron to proton ratio from that observed locally are unlikely along a line of sight. The differences in the predicted and observed γ-ray intensities in the galactic plane are small. However, in the polar direction, the predicted γ-ray flux using the radio data is approx.6 times larger than that actually observed. This is indicative of the fact that the radio emissivity is considerably thicker than the γ-ray emissivity disk, and the cosmic-ray electron population extends beyond the gaseous disk of the Galaxy. This technique of estimating the γ-ray intensity using the radio data is compared with the usual technique which employs estimates of the column density of hydrogen

Analysis of the correlation between γ-ray and radio emissions from γ-ray loud Blazar using the discrete correlation function

International Nuclear Information System (INIS)

Cheng Yong; Zhang Xiong; Wu Lin; Mao Weiming; You Lisha

2006-01-01

The authors collect 119 γ-ray-loud Blazar (97 flat spectrum radio quasars (FSRQs) and 22 BL Lacertae objects (BL Lac)), and investigate respectively the correlation between the γ-ray emission (maximum, minimum, and average data) at 1 GeV and the radio emission at 8.4 GHz by discrete correlation function (DCF) method. Our main results are as follows: there is good correlation between the γ-ray in high state and average state and radio emissions for the whole 119 Blazar and 97 FSRQs. And there are no correlation between γ-ray emission and radio emission in low state. Our result shows that the γ-rays are associated with the radio emission from the jet, and that the γ-ray emission is likely to have come from the synchrotron self-compton model (SSC) process in this case. (authors)

Near Earth space sporadic radio emission busts occurring during sunrise

Science.gov (United States)

Dudnik, A. V.; Zaljubovsky, I. I.; Kartashev, V. M.; Lasarev, A. V.; Shmatko, E. S.

1985-01-01

During the period of low solar activity at sunrise the effect of sporadic high frequency near Earth space radio emission was experimentally discovered at middle latitudes. The possible mechanism of its origin is discussed.

Structure of the radio emission from the NGC 1579/LkH. cap alpha. 101 region

Energy Technology Data Exchange (ETDEWEB)

Brown, R L [National Radio Astronomy Observatory, Charlottesville, Va. (USA); Broderick, J J; Knapp, G R

1976-06-01

Radio-frequency observations at 3.7 and 11 cm of the NGC 1579/LkH..cap alpha..101 region show that the radio emission arises in a compact, < 1'' core concentric with a more extended approximately 1' emission region. At these wavelengths the compact component is optically thick, with a spectrum increasing as ..nu.., whereas the extended region is optically thin and contributes at least 80 per cent of the total flux density. LkH..cap alpha..101 appears to be the source of excitation for all of the radio emission; this result, together with the total infrared luminosity, suggests that an appropriate spectral classification for LkH..cap alpha..101 is B1 IIe.

THE SCALING RELATIONS AND THE FUNDAMENTAL PLANE FOR RADIO HALOS AND RELICS OF GALAXY CLUSTERS

International Nuclear Information System (INIS)

Yuan, Z. S.; Han, J. L.; Wen, Z. L.

2015-01-01

Diffuse radio emission in galaxy clusters is known to be related to cluster mass and cluster dynamical state. We collect the observed fluxes of radio halos, relics, and mini-halos for a sample of galaxy clusters from the literature, and calculate their radio powers. We then obtain the values of cluster mass or mass proxies from previous observations, and also obtain the various dynamical parameters of these galaxy clusters from optical and X-ray data. The radio powers of relics, halos, and mini-halos are correlated with the cluster masses or mass proxies, as found by previous authors, while the correlations concerning giant radio halos are in general the strongest. We found that the inclusion of dynamical parameters as the third dimension can significantly reduce the data scatter for the scaling relations, especially for radio halos. We therefore conclude that the substructures in X-ray images of galaxy clusters and the irregular distributions of optical brightness of member galaxies can be used to quantitatively characterize the shock waves and turbulence in the intracluster medium responsible for re-accelerating particles to generate the observed diffuse radio emission. The power of radio halos and relics is correlated with cluster mass proxies and dynamical parameters in the form of a fundamental plane

Full PIC simulations of solar radio emission

Science.gov (United States)

Sgattoni, A.; Henri, P.; Briand, C.; Amiranoff, F.; Riconda, C.

2017-12-01

Solar radio emissions are electromagnetic (EM) waves emitted in the solar wind plasma as a consequence of electron beams accelerated during solar flares or interplanetary shocks such as ICMEs. To describe their origin, a multi-stage model has been proposed in the 60s which considers a succession of non-linear three-wave interaction processes. A good understanding of the process would allow to infer the kinetic energy transfered from the electron beam to EM waves, so that the radio waves recorded by spacecraft can be used as a diagnostic for the electron beam.Even if the electrostatic problem has been extensively studied, full electromagnetic simulations were attempted only recently. Our large scale 2D-3V electromagnetic PIC simulations allow to identify the generation of both electrostatic and EM waves originated by the succession of plasma instabilities. We tested several configurations varying the electron beam density and velocity considering a background plasma of uniform density. For all the tested configurations approximately 105 of the electron-beam kinetic energy is transfered into EM waves emitted in all direction nearly isotropically. With this work we aim to design experiments of laboratory astrophysics to reproduce the electromagnetic emission process and test its efficiency.

Radio astronomy

Energy Technology Data Exchange (ETDEWEB)

Nagnibeda, V.G.

1981-01-01

The history of radio astronomical observations at the Astronomical Observatory of Leningrad State University is reviewed. Various facilities are described, and methods and instruments used are discussed. Some results are summarized for radio observations of the sun, including observations of local sources of solar radio emission, the absolute solar radio flux, and radio emission from filaments and prominences.

Automated detection of extended sources in radio maps: progress from the SCORPIO survey

Science.gov (United States)

Riggi, S.; Ingallinera, A.; Leto, P.; Cavallaro, F.; Bufano, F.; Schillirò, F.; Trigilio, C.; Umana, G.; Buemi, C. S.; Norris, R. P.

2016-08-01

Automated source extraction and parametrization represents a crucial challenge for the next-generation radio interferometer surveys, such as those performed with the Square Kilometre Array (SKA) and its precursors. In this paper, we present a new algorithm, called CAESAR (Compact And Extended Source Automated Recognition), to detect and parametrize extended sources in radio interferometric maps. It is based on a pre-filtering stage, allowing image denoising, compact source suppression and enhancement of diffuse emission, followed by an adaptive superpixel clustering stage for final source segmentation. A parametrization stage provides source flux information and a wide range of morphology estimators for post-processing analysis. We developed CAESAR in a modular software library, also including different methods for local background estimation and image filtering, along with alternative algorithms for both compact and diffuse source extraction. The method was applied to real radio continuum data collected at the Australian Telescope Compact Array (ATCA) within the SCORPIO project, a pathfinder of the Evolutionary Map of the Universe (EMU) survey at the Australian Square Kilometre Array Pathfinder (ASKAP). The source reconstruction capabilities were studied over different test fields in the presence of compact sources, imaging artefacts and diffuse emission from the Galactic plane and compared with existing algorithms. When compared to a human-driven analysis, the designed algorithm was found capable of detecting known target sources and regions of diffuse emission, outperforming alternative approaches over the considered fields.

Diffuse γ-ray emission from galactic pulsars

International Nuclear Information System (INIS)

Calore, F.; Di Mauro, M.; Donato, F.

2014-01-01

Millisecond pulsars (MSPs) are old fast-spinning neutron stars that represent the second most abundant source population discovered by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi). As guaranteed γ-ray emitters, they might contribute non-negligibly to the diffuse emission measured at high latitudes by Fermi-LAT (i.e., the Isotropic Diffuse γ-Ray Background (IDGRB)), which is believed to arise from the superposition of several components of galactic and extragalactic origin. Additionally, γ-ray sources also contribute to the anisotropy of the IDGRB measured on small scales by Fermi-LAT. In this manuscript we aim to assess the contribution of the unresolved counterpart of the detected MSPs population to the IDGRB and the maximal fraction of the measured anisotropy produced by this source class. To this end, we model the MSPs' spatial distribution in the Galaxy and the γ-ray emission parameters by considering observational constraints coming from the Australia Telescope National Facility pulsar catalog and the Second Fermi-LAT Catalog of γ-ray pulsars. By simulating a large number of MSP populations through a Monte Carlo simulation, we compute the average diffuse emission and the anisotropy 1σ upper limit. We find that the emission from unresolved MSPs at 2 GeV, where the peak of the spectrum is located, is at most 0.9% of the measured IDGRB above 10° in latitude. The 1σ upper limit on the angular power for unresolved MSP sources turns out to be about a factor of 60 smaller than Fermi-LAT measurements above 30°. Our results indicate that this galactic source class represents a negligible contributor to the high-latitude γ-ray sky and confirm that most of the intensity and geometrical properties of the measured diffuse emission are imputable to other extragalactic source classes (e.g., blazars, misaligned active galactic nuclei, or star-forming galaxies). Nevertheless, because MSPs are more concentrated toward the

The Chandra M10l Megasecond: Diffuse Emission

Science.gov (United States)

Kuntz, K. D.; Snowden, S. L.

2009-01-01

Because MIOl is nearly face-on, it provides an excellent laboratory in which to study the distribution of X-ray emitting gas in a typical late-type spiral galaxy. We obtained a Chandra observation with a cumulative exposure of roughly 1 Ms to study the diffuse X-ray emission in MlOl. The bulk of the X-ray emission is correlated with the star formation traced by the FUV emission. The global FUV/Xray correlation is non-linear (the X-ray surface brightness is roughly proportional to the square root of the FUV surface brightness) and the small-scale correlation is poor, probably due to the delay between the FUV emission and the X-ray production ill star-forming regions. The X-ray emission contains only minor contributions from unresolved stars (approximates less than 3%), unresolved X-ray point sources (approximates less than 4%), and individual supernova remnants (approximates 3%). The global spectrum of the diffuse emission can be reasonably well fitted with a three component thermal model, but the fitted temperatures are not unique; many distributions of emission measure can produce the same temperatures when observed with the current CCD energy resolution. The spectrum of the diffuse emission depends on the environment; regions with higher X-ray surface brightnesses have relatively stronger hard components, but there is no significant evidence that the temperatures of the emitting components increase with surface brightness.

Probing Atmospheric Electric Fields through Radio Emission from Cosmic-Ray-Induced Air Showers

NARCIS (Netherlands)

Scholten, Olaf; Trinh, Gia; Buitink, Stijn; Corstanje, Arthur; Ebert, Ute; Enriquez, Emilio; Falcke, Heino; Hoerandel, Joerg; Nelles, Anna; Schellart, Pim; Rachen, Joerg; Rutjes, Casper; ter Veen, Sander; Rossetto, Laura; Thoudam, Satyendra

2016-01-01

Energetic cosmic rays impinging on the atmosphere create a particle avalanche called an extensive air shower. In the leading plasma of this shower electric currents are induced that generate coherent radio wave emission that has been detected with LOFAR, a large and dense array of simple radio

How expanded ionospheres of Hot Jupiters can prevent escape of radio emission generated by the cyclotron maser instability

Science.gov (United States)

Weber, C.; Lammer, H.; Shaikhislamov, I. F.; Chadney, J. M.; Khodachenko, M. L.; Grießmeier, J.-M.; Rucker, H. O.; Vocks, C.; Macher, W.; Odert, P.; Kislyakova, K. G.

2017-08-01

We present a study of plasma conditions in the atmospheres of the Hot Jupiters HD 209458b and HD 189733b and for an HD 209458b like planet at orbit locations between 0.2 and 1 au around a Sun-like star. We discuss how these conditions influence the radio emission we expect from their magnetospheres. We find that the environmental conditions are such that the cyclotron maser instability (CMI), the process responsible for the generation of radio waves at magnetic planets in the Solar system, most likely will not operate at Hot Jupiters. Hydrodynamically expanding atmospheres possess extended ionospheres whose plasma densities within the magnetosphere are so large that the plasma frequency is much higher than the cyclotron frequency, which contradicts the condition for the production of radio emission and prevents the escape of radio waves from close-in exoplanets at distances produce radio emission. However, even if the CMI could operate, the extended ionospheres of Hot Jupiters are too dense to allow the radio emission to escape from the planets.

Solar energetic particles and radio burst emission

Czech Academy of Sciences Publication Activity Database

Miteva, R.; Samwel, S. W.; Krupař, Vratislav

2017-01-01

Roč. 7 (2017), č. článku A37. ISSN 2115-7251 R&D Projects: GA ČR(CZ) GJ17-06818Y Institutional support: RVO:68378289 Keywords : solar energetic particles * solar radio burst emission * solar cycle Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.446, year: 2016 https://www.swsc-journal.org/ articles /swsc/abs/2017/01/swsc170028/swsc170028.html

THE JET POWER AND EMISSION-LINE CORRELATIONS OF RADIO-LOUD OPTICALLY SELECTED QUASARS

International Nuclear Information System (INIS)

Punsly, Brian; Zhang Shaohua

2011-01-01

In this Letter, the properties of the extended radio emission form Sloan Digital Sky Survey Data Release 7 quasars with 0.4 20-30 kpc). The frequency of quasars with FR II level extended radio emission is ∼2.3% and >0.4% of quasars have FR I level extended radio emission. The lower limit simply reflects the flux density limit of the survey. The distribution of the long-term time-averaged jet powers of these quasars, Q-bar , has a broad peak ∼3 x 10 44 erg s -1 that turns over below 10 44 erg s -1 and sources above 10 45 erg s -1 are extremely rare. It is found that the correlation between the bolometric (total thermal) luminosity of the accretion flow, L bol , and Q-bar is not strong. The correlation of Q-bar with narrow line luminosity is stronger than the correlation with broad line luminosity and the continuum luminosity. It is therefore concluded that previous interpretations of correlations of Q-bar with narrow line strengths in radio galaxies as a direct correlation of jet power and accretion power have been overstated. It is explained why this interpretation mistakenly overlooks the sizeable fraction of sources with weak accretion luminosity and powerful jets discovered by Ogle et al.

Milliarcsecond Imaging of the Radio Emission from the Quasar with the Most Massive Black Hole at Reionization

Energy Technology Data Exchange (ETDEWEB)

Wang, Ran; Wu, Xue-Bing; Jiang, Linhua [Kavli Institute of Astronomy and Astrophysics at Peking University, No. 5 Yiheyuan Road, Haidian District, Beijing 100871 (China); Momjian, Emmanuel; Carilli, Chris L. [National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801 (United States); Fan, Xiaohui [Steward Observatory, University of Arizona, 933 N Cherry Avenue, Tucson, AZ 85721 (United States); Walter, Fabian [Max-Planck-Institute for Astronomy, Königsstuhl 17, D-69117 Heidelberg (Germany); Strauss, Michael A. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Wang, Feige [Department of Astronomy, School of Physics, Peking University, No. 5 Yiheyuan Road, Haidian District, Beijing 100871 (China)

2017-02-01

We report Very Long Baseline Array (VLBA) observations of the 1.5 GHz radio continuum emission of the z = 6.326 quasar SDSS J010013.02+280225.8 (hereafter J0100+2802). J0100+2802 is by far the most optically luminous and is a radio-quiet quasar with the most massive black hole known at z > 6. The VLBA observations have a synthesized beam size of 12.10 mas ×5.36 mas (FWHM), and detected the radio continuum emission from this object with a peak surface brightness of 64.6 ± 9.0 μ Jy beam{sup −1} and a total flux density of 88 ± 19 μ Jy. The position of the radio peak is consistent with that from SDSS in the optical and Chandra in the X-ray. The radio source is marginally resolved by the VLBA observations. A 2D Gaussian fit to the image constrains the source size to (7.1 ± 3.5) mas × (3.1 ± 1.7) mas. This corresponds to a physical scale of (40 ± 20) pc × (18 ± 10) pc. We estimate the intrinsic brightness temperature of the VLBA source to be T {sub B} = (1.6 ± 1.2) × 10{sup 7} K. This is significantly higher than the maximum value in normal star-forming galaxies, indicating an active galactic nucleus (AGN) origin for the radio continuum emission. However, it is also significantly lower than the brightness temperatures found in highest-redshift radio-loud quasars. J0100+2802 provides a unique example for studying the radio activity in optically luminous and radio-quiet AGNs in the early universe. Further observations at multiple radio frequencies will accurately measure the spectral index and address the dominant radiation mechanism of the radio emission.

AXIAL RATIO OF EDGE-ON SPIRAL GALAXIES AS A TEST FOR BRIGHT RADIO HALOS

International Nuclear Information System (INIS)

Singal, J.; Jones, E.; Dunlap, H.; Kogut, A.

2015-01-01

We use surface brightness contour maps of nearby edge-on spiral galaxies to determine whether extended bright radio halos are common. In particular, we test a recent model of the spatial structure of the diffuse radio continuum by Subrahmanyan and Cowsik which posits that a substantial fraction of the observed high-latitude surface brightness originates from an extended Galactic halo of uniform emissivity. Measurements of the axial ratio of emission contours within a sample of normal spiral galaxies at 1500 MHz and below show no evidence for such a bright, extended radio halo. Either the Galaxy is atypical compared to nearby quiescent spirals or the bulk of the observed high-latitude emission does not originate from this type of extended halo. (letters)

X-RAY AND RADIO EMISSION FROM TYPE IIn SUPERNOVA SN 2010jl

Energy Technology Data Exchange (ETDEWEB)

Chandra, Poonam [National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune University Campus, Pune 411 007 (India); Chevalier, Roger A. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States); Chugai, Nikolai [Institute of Astronomy of Russian Academy of Sciences, Pyatnitskaya St. 48, 109017 Moscow (Russian Federation); Fransson, Claes [Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, SE-106 91 Stockholm (Sweden); Soderberg, Alicia M., E-mail: poonam@ncra.tifr.res.in [Smithsonian Astrophysical Observatory, 60 Garden St., MS-20, Cambridge, MA 02138 (United States)

2015-09-01

We present all X-ray and radio observations of the Type IIn supernova SN 2010jl. The X-ray observations cover a period up to day 1500 with Chandra, XMM-Newton, NuSTAR, and Swift-X-ray Telescope (XRT). The Chandra observations after 2012 June, the XMM-Newton observation in 2013 November, and most of the Swift-XRT observations until 2014 December are presented for the first time. All the spectra can be fitted by an absorbed hot thermal model except for Chandra spectra on 2011 October and 2012 June when an additional component is needed. Although the origin of this component is uncertain, it is spatially coincident with the supernova and occurs when there are changes to the supernova spectrum in the energy range close to that of the extra component, indicating that the emission is related to the supernova. The X-ray light curve shows an initial plateau followed by a steep drop starting at day ∼300. We attribute the drop to a decrease in the circumstellar density. The column density to the X-ray emission drops rapidly with time, showing that the absorption is in the vicinity of the supernova. We also present Very Large Array radio observations of SN 2010jl. Radio emission was detected from SN 2010jl from day 570 onwards. The radio light curves and spectra suggest that the radio luminosity was close to its maximum at the first detection. The velocity of the shocked ejecta derived assuming synchrotron self-absorption is much less than that estimated from the optical and X-ray observations, suggesting that free–free absorption dominates.

Interplanetary radio storms. II - Emission levels and solar wind speed in the range 0.05-0.8 AU

Science.gov (United States)

Bougeret, J.-L.; Fainberg, J.; Stone, R. G.

1984-01-01

Storms of interplanetary type III radio bursts (IP storms) are commonly observed in the interplanetary medium by the ISEE-3 radio instrument. This instrument has the capability of accurately determining the arrival direction of the radio emission. At each observing frequency, the storm radio sources are tracked as they cross the line-of-sight to the sun. Using a simple model, the emission levels are determined at a number of radio frequencies for four separate storms. The IP storm radiation is found to occur in regions of enhanced density at levels of 0.05 to 0.8 AU. The density in these enhancements falls off faster than R(-2). The solar wind speed in the storm region is also measured. The analysis is consistent with steady conditions in the storm region during a few days around the III storm burst radio emission at the harmonic of the local plasma frequency.

Spectroscopic and polarimetric study of radio-quiet weak emission line quasars

Science.gov (United States)

Kumar, Parveen; Chand, Hum; Gopal-Krishna; Srianand, Raghunathan; Stalin, Chelliah Subramonian; Petitjean, Patrick

2018-04-01

A small subset of optically selected radio-quiet QSOs with weak or no emission lines may turn out to be the elusive radio-quiet BL Lac objects, or simply be radio-quiet QSOs with an infant/shielded broad line region (BLR). High polarisation (p > 3-4%), a hallmark of BL Lacs, can be used to test whether some optically selected ‘radio-quiet weak emission line QSOs’ (RQWLQs) show a fractional polarisation high enough to qualify as radio-quiet analogues of BL Lac objects. To check this possibility, we have made optical spectral and polarisation measurements of a sample of 19 RQWLQs. Out of these, only 9 sources show a non-significant proper motion (hence very likely extragalactic) and only two of them are found to have p > 1%. For these two RQWLQs, namely J142505.59+035336.2 and J154515.77+003235.2, we found the highest polarization to be 1.59±0.53%, which is again too low to classify them as (radio-quiet) BL Lacs, although one may recall that even genuine BL Lacs sometimes appear weakly polarised. We also present a statistical comparison of the optical spectral index, for a sample of 45 RQWLQs with redshift-luminosity matched control samples of 900 QSOs and an equivalent sample of 120 blazars, assembled from the literature. The spectral index distribution of RQWLQs is found to differ, at a high significance level, from that of blazars. This, too, is consistent with the common view that the mechanism of the central engine in RQWLQs, as a population, is close to that operating in normal QSOs and the primary difference between them is related to the BLR.

THE COMPLEX NORTH TRANSITION REGION OF CENTAURUS A: RADIO STRUCTURE

Energy Technology Data Exchange (ETDEWEB)

Neff, Susan G. [NASA' s Goddard Space Flight Center, Laboratory for Observational Cosmology, Mail Code 665, Greenbelt, MD 20771 (United States); Eilek, Jean A. [Physics Department, New Mexico Tech, Socorro, NM 87801 (United States); Owen, Frazer N., E-mail: susan.g.neff@nasa.gov [National Radio Astronomy Observatory, P.O. Box O,  Socorro, NM 87801 (United States)

2015-04-01

We present deep radio images of the inner ∼50 kpc of Centaurus A, taken with the Karl G. Jansky Very Large Array at 90 cm. We focus on the Transition Regions between the inner galaxy—including the active nucleus, inner radio lobes, and star-forming disk—and the outer radio lobes. We detect previously unknown extended emission around the Inner Lobes, including radio emission from the star-forming disk. We find that the radio-loud part of the North Transition Region (NTR), known as the North Middle Lobe, is significantly overpressured relative to the surrounding interstellar medium. We see no evidence for a collimated flow from the active galactic nucleus through this region. Our images show that the structure identified by Morganti et al. as a possible large-scale jet appears to be part of a narrow ridge of emission within the broader, diffuse, radio-loud region. This knotty radio ridge is coincident with other striking phenomena: compact X-ray knots, ionized gas filaments, and streams of young stars. Several short-lived phenomena in the NTR, as well as the frequent re-energization required by the Outer Lobes, suggest that energy must be flowing through both Transition Regions at the present epoch. We suggest that the energy flow is in the form of a galactic wind.

Pulsed Gamma Rays from the Original Millisecond and Black Widow Pulsars: A Case for Caustic Radio Emission?

Science.gov (United States)

Guillemot, L.; Johnson, T. J.; Venter, C.; Kerr, M.; Pancrazi, B.; Livingstone, M.; Janssen, G. H.; Jaroenjittichai, P.; Kramer, M.; Cognard, I.;

Sky-distribution of intensity of synchrotron radio emission of relativistic electrons trapped in Earth’s magnetic field

Directory of Open Access Journals (Sweden)

Klimenko V.V.

2017-12-01

Full Text Available This paper presents the calculations of synchrotron radio emission intensity from Van Allen belts with Gaussian space distribution of electron density across L-shells of a dipole magnetic field, and with Maxwell’s relativistic electron energy distribution. The results of these calculations come to a good agreement with measurements of the synchrotron emission intensity of the artificial radiation belt’s electrons during the Starfish nuclear test. We have obtained two-dimensional distributions of radio brightness in azimuth — zenith angle coordinates for an observer on Earth’s surface. The westside and eastside intensity maxima exceed several times the maximum level of emission in the meridian plane. We have also constructed two-dimensional distributions of the radio emission intensity in decibels related to the background galactic radio noise level. Isotropic fluxes of relativistic electrons (Е~1 MeV should be more than 107 cm–2s–1 for the synchrotron emission intensity in the meridian plane to exceed the cosmic noise level by 0.1 dB (riometer sensitivity threshold.

The pulsar contribution to the diffuse galactic gamma-ray emission

DEFF Research Database (Denmark)

Pohl, M.; Kanbach, G.; Hunter, S.D.

1997-01-01

There is active interest in the extent to which unresolved gamma-ray pulsars contribute to the Galactic diffuse emission, and in whether unresolved gamma-ray pulsars could be responsible for the excess of diffuse Galactic emission above 1 GeV that has been observed by EGRET. The diffuse gamma......-ray intensity due to unresolved pulsars is directly linked to the number of objects that should be observed in the EGRET data. We can therefore use our knowledge of the unidentified EGRET sources to constrain model parameters like the pulsar birthrate and their beaming angle. This analysis is based only...... on the properties of the six pulsars that have been identified in the EGRET data and is independent of choice of a pulsar emission model. We find that pulsars contribute very little to the diffuse emission at lower energies, whereas above 1 GeV they can account for 18% of the observed intensity in selected regions...

PHYSICAL CONSTRAINTS ON FAST RADIO BURSTS

Energy Technology Data Exchange (ETDEWEB)

Luan, Jing; Goldreich, Peter, E-mail: jingluan@caltech.edu [California Institute of Technology, Pasadena, CA 91125 (United States)

2014-04-20

Fast radio bursts (FRBs) are isolated, ms radio pulses with dispersion measure (DM) of order 10{sup 3} pc cm{sup –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.

PHYSICAL CONSTRAINTS ON FAST RADIO BURSTS

International Nuclear Information System (INIS)

Luan, Jing; Goldreich, Peter

2014-01-01

Fast radio bursts (FRBs) are isolated, ms radio pulses with dispersion measure (DM) of order 10 3 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

Modelling of radio emission from cosmic ray air showers

Science.gov (United States)

Ludwig, Marianne

2011-06-01

Cosmic rays entering the Earth's atmosphere induce extensive air showers consisting of up to billions of secondary particles. Among them, a multitude of electrons and positrons are generated. These get deflected in the Earth's magnetic field, creating time-varying transverse currents. Thereby, the air shower emits coherent radiation in the MHz frequency range measured by radio antenna arrays on the ground such as LOPES at the KIT. This detection method provides a possibility to study cosmic rays with energies above 1017 eV. At this time, the radio technique undergoes the change from prototype experiments to large scale application. Thus, a detailed understanding of the radio emission process is needed more than ever. Before starting this work, different models made conflicting predictions on the pulse shape and the amplitude of the radio signal. It turned out that a radiation component caused by the variation of the number of charged particles within the air shower was missed in several models. The Monte Carlo code REAS2 superposing the radiation of the individual air shower electrons and positrons was one of those. At this time, it was not known how to take the missing component into account. For REAS3, we developed and implemented the endpoint formalism, a universal approach, to calculate the radiation from each single particle. For the first time, we achieve a good agreement between REAS3 and MGMR, an independent and completely different simulation approach. In contrast to REAS3, MGMR is based on a macroscopic approach and on parametrisations of the air shower. We studied the differences in the underlying air shower models to explain the remaining deviations. For comparisons with LOPES data, we developed a new method which allows "top-down" simulations of air showers. From this, we developed an air shower selection criterion based on the number of muons measured with KASCADE to take shower-to-shower fluctuations for a single event analysis into account. With

Radio stars

International Nuclear Information System (INIS)

Hjellming, R.M.; Gibson, D.M.

1985-01-01

Studies of stellar radio emission became an important field of research in the 1970's and have now expanded to become a major area of radio astronomy with the advent of new instruments such as the Very Large Array in New Mexico and transcontinental telescope arrays. This volume contains papers from the workshop on stellar continuum radio astronomy held in Boulder, Colorado, and is the first book on the rapidly expanding field of radio emission from stars and stellar systems. Subjects covered include the observational and theoretical aspects of stellar winds from both hot and cool stars, radio flares from active double star systems and red dwarf stars, bipolar flows from star-forming regions, and the radio emission from X-ray binaries. (orig.)

Isotropic radio background from quark nugget dark matter

Energy Technology Data Exchange (ETDEWEB)

Lawson, Kyle; Zhitnitsky, Ariel R., E-mail: arz@physics.ubc.ca

2013-07-09

Recent measurements by the ARCADE2 experiment unambiguously show an excess in the isotropic radio background at frequencies below the GHz scale. We argue that this excess may be a natural consequence of the interaction of visible and dark matter in the early universe if the dark matter consists of heavy nuggets of quark matter. Explanation of the observed radio band excess requires the introduction of no new parameters, rather we exploit the same dark matter model and identical normalization parameters to those previously used to explain other excesses of diffuse emission from the centre of our galaxy. These previously observed excesses include the WMAP Haze of GHz radiation, keV X-ray emission and MeV gamma-ray radiation.

Isotropic radio background from quark nugget dark matter

International Nuclear Information System (INIS)

Lawson, Kyle; Zhitnitsky, Ariel R.

2013-01-01

Recent measurements by the ARCADE2 experiment unambiguously show an excess in the isotropic radio background at frequencies below the GHz scale. We argue that this excess may be a natural consequence of the interaction of visible and dark matter in the early universe if the dark matter consists of heavy nuggets of quark matter. Explanation of the observed radio band excess requires the introduction of no new parameters, rather we exploit the same dark matter model and identical normalization parameters to those previously used to explain other excesses of diffuse emission from the centre of our galaxy. These previously observed excesses include the WMAP Haze of GHz radiation, keV X-ray emission and MeV gamma-ray radiation

Problems with interpreting the radio emission from hot stars

International Nuclear Information System (INIS)

Underhill, A.B.

1985-01-01

The hypothesis that the radio emission from a hot star is due solely to bremsstrahlung in a spherically symmetric wind flowing at a constant velocity and the constraint that the wind be transparent enough to allow the stationary photosphere to be seen, place a limit on mass loss/v (M/V). The constraint that the momentum in the wind be provided by the radiation field places a limit on Mv. It is noted that both constraints are satisfied by the usually deduced values of M and v(infinity) for OB supergiants. The case for early O stars is marginal, while for Wolf-Rayet stars M/v and Mv are too large to satisfy the several hypotheses usually made. The trouble is due to M being too large by at least a factor 10. It is noted that postulating that part of the radio flux from Wolf-Rayet stars is caused by processes in a low-density magnetized plasma provides a solution to the dilemma. This solution offers advantages when accounting for the emission lines of Wolf-Rayet stars. (orig.)

Radio emission in peculiar galaxies

Science.gov (United States)

Demellorabaca, Dulia F.; Abraham, Zulema

1990-01-01

During the last decades a number of surveys of peculiar galaxies have been carried out and accurate positions become available. Since peculiarities are a possible evidence of radio emission (Wright, 1974; Sulentic, 1976; Stocke et al., 1978), the authors selected a sample of 24 peculiar galaxies with optical jet-like features or extensions in different optical catalogues, mainly the Catalogue of Southern Peculiar Galaxies and Associations (Arp and Madore, 1987) and the ESO/Uppsala Survey of the ESO(B) Atlas (Lauberts, 1982) for observation at the radio continuum frequency of 22 GHz. The sample is listed in a table. Sol (1987) studied this sample and concluded that the majority of the jet-like features seem to admit an explanation in terms of interactive galaxies with bridges and/or tails due to tidal effects. Only in a few cases do the jets seem to be possibly linked to some nuclear activity of the host galaxy. The observations were made with the 13.7m-radome enclosed Itapetinga Radiotelescope (HPBW of 4.3 arcmin), in Brazil. The receiver was a 1 GHz d.s.b. super-heterodine mixer operated in total-power mode, with a system temperature of approximately 800 K. The observational technique consisted in scans in right ascention, centralized in the optical position of the galaxy. The amplitude of one scan was 43 arcmin, and its duration time was 20 seconds. The integration time was at least 2 hours (12 ten-minute observations) and the sensibility limit adopted was an antenna temperature greater than 3 times the r.m.s. error of the baseline determination. Virgo A was used as the calibrator source. Three galaxies were detected for the first time as radio sources and four other known galaxies at low frequencies had their flux densities measured at 22 GHz. The results for these sources are presented.

Radio emissions from pulsar companions: a refutable explanation for galactic transients and fast radio bursts

Science.gov (United States)

Mottez, F.; Zarka, P.

2014-09-01

Context. The six known highly dispersed fast radio bursts are attributed to extragalactic radio sources that are of unknown origin but extremely energetic. We propose here a new explanation that does not require an extreme release of energy and involves a body (planet, asteroid, white dwarf) orbiting an extragalactic pulsar. Aims: We investigate a theory of radio waves associated with such pulsar-orbiting bodies. We focus our analysis on the waves emitted from the magnetic wake of the body in the pulsar wind. After deriving their properties, we compare them with the observations of various transient radio signals to determine whether they could originate from pulsar-orbiting bodies. Methods: The analysis is based on the theory of Alfvén wings: for a body immersed in a pulsar wind, a system of two stationary Alfvén waves is attached to the body, provided that the wind is highly magnetised. When they are destabilised through plasma instabilities, Alfvén wings can be the locus of strong radio sources that are convected with the pulsar wind. By assuming a cyclotron maser instability operating in the Alfvén wings, we make predictions about the shape, frequencies, and brightness of the resulting radio emissions. Results: Because of the beaming by relativistic aberration, the signal is seen only when the companion is perfectly aligned between its parent pulsar and the observer, as is the case for occultations. For pulsar winds with a high Lorentz factor (≥104), the whole duration of the radio event does not exceed a few seconds, and it is composed of one to four peaks that last a few milliseconds each and are detectable up to distances of several Mpc. The Lorimer burst, the three isolated pulses of PSR J1928+15, and the recently detected fast radio bursts are all compatible with our model. According to it, these transient signals should repeat periodically with the companion's orbital period. Conclusions: The search of pulsar-orbiting bodies could be an exploration

STUDY OF CALIBRATION OF SOLAR RADIO SPECTROMETERS AND THE QUIET-SUN RADIO EMISSION

Energy Technology Data Exchange (ETDEWEB)

Tan, Chengming; Yan, Yihua; Tan, Baolin; Fu, Qijun; Liu, Yuying [Key Laboratory of Solar Activity, National Astronomical Observatories of Chinese Academy of Sciences, Datun Road A20, Chaoyang District, Beijing 100012 (China); Xu, Guirong [Hubei Key Laboratory for Heavy Rain Monitoring and Warning Research, Institute of Heavy Rain, China Meteorological Administration, Wuhan 430205 (China)

2015-07-20

This work presents a systematic investigation of the influence of weather conditions on the calibration errors by using Gaussian fitness, least chi-square linear fitness, and wavelet transform to analyze the calibration coefficients from observations of the Chinese Solar Broadband Radio Spectrometers (at frequency bands of 1.0–2.0 GHz, 2.6–3.8 GHz, and 5.2–7.6 GHz) during 1997–2007. We found that calibration coefficients are influenced by the local air temperature. Considering the temperature correction, the calibration error will reduce by about 10%–20% at 2800 MHz. Based on the above investigation and the calibration corrections, we further study the radio emission of the quiet Sun by using an appropriate hybrid model of the quiet-Sun atmosphere. The results indicate that the numerical flux of the hybrid model is much closer to the observation flux than that of other ones.

The Models for Radio Emission from Pulsars – The Outstanding issues

Indian Academy of Sciences (India)

tribpo

in section 4, where existing models for pulsar radio emission are also reviewed. ... pair plasma flowing outward along open magnetic field lines from the polar caps ..... A reactive instability involves an intrinsically growing, phase-coherent wave.

TURBULENCE AND RADIO MINI-HALOS IN THE SLOSHING CORES OF GALAXY CLUSTERS

International Nuclear Information System (INIS)

ZuHone, J. A.; Markevitch, M.; Brunetti, G.; Giacintucci, S.

2013-01-01

A number of relaxed, cool-core galaxy clusters exhibit diffuse, steep-spectrum radio sources in their central regions, known as radio mini-halos. It has been proposed that the relativistic electrons responsible for the emission have been reaccelerated by turbulence generated by the sloshing of the cool core gas. We present a high-resolution MHD simulation of gas sloshing in a galaxy cluster coupled with subgrid simulations of relativistic electron acceleration to test this hypothesis. Our simulation shows that the sloshing motions generate turbulence on the order of δv ∼ 50-200 km s –1 on spatial scales of ∼50-100 kpc and below in the cool core region within the envelope of the sloshing cold fronts, whereas outside the cold fronts, there is negligible turbulence. This turbulence is potentially strong enough to reaccelerate relativistic electron seeds (with initial γ ∼ 100-500) to γ ∼ 10 4 via damping of magnetosonic waves and non-resonant compression. The seed electrons could remain in the cluster from, e.g., past active galactic nucleus activity. In combination with the magnetic field amplification in the core, these electrons then produce diffuse radio synchrotron emission that is coincident with the region bounded by the sloshing cold fronts, as indeed observed in X-rays and the radio. The result holds for different initial spatial distributions of pre-existing relativistic electrons. The power and the steep spectral index (α ≈ 1-2) of the resulting radio emission are consistent with observations of mini-halos, though the theoretical uncertainties of the acceleration mechanisms are high. We also produce simulated maps of inverse-Compton hard X-ray emission from the same population of relativistic electrons.

Ground and space observations of medium frequency auroral radio emissions

Science.gov (United States)

Broughton, Matthew C.

The auroral zone is a rich source of natural radio emissions that can be observed in space and at ground-level. By studying these waves, scientists can gain insight into the plasma processes that generate them and use the near-Earth space environment as a large-scale plasma physics laboratory. This thesis uses both ground-level and in situ observations to study two kinds of natural radio emissions. First, we report observations of a new kind of auroral radio emission. The waves have frequencies ranging from 1.3-2.2 MHz, bandwidths ranging from 90-272 kHz, and durations ranging from 16-355 s. Spectral analysis of the waveform data has revealed that the emission has a complex combination of at least three kinds of fine structures. For model auroral electron distributions, calculations indicate that Langmuir waves could be excited at frequencies consistent with observations. The remainder of the thesis discusses auroral medium frequency (MF) burst, an impulsive, broadband natural radio emission observed at ground-level within a few minutes of local substorm onset. LaBelle [2011] proposed that MF burst originates as Langmuir/Z-mode waves on the topside of the ionosphere that subsequently mode convert to L-mode waves and propagate to ground-level. Using continuous waveform measurements and combined observations with the Sondrestrom Incoherent Scatter Radar, we have performed two tests of this mechanism. The results of these tests are consistent with the mechanism described in LaBelle [2011]. A survey of 8,624 half-orbits of the DEMETER spacecraft has revealed 68 observations of bursty MF waves. We have compared the wave properties of these waves to those of MF burst and have found that although it is uncertain, the balance of the evidence suggests that the bursty MF waves observed with DEMETER are the same phenomenon as the ground-level MF burst. Finally, we have used numerical simulations to model both the fine structure of MF burst and to estimate the attenuation the

Radio-emission of pre-main sequence stars of the Rho Ophiuchi cloud: observations and interpretation

International Nuclear Information System (INIS)

Andre, P.

1987-11-01

Observations of the radio continuum emission of a young star population have been made at VLA on the whole molecular cloud Rho Ophiuchi, one of the closest site of star formation. A dozen of stellar sources have been detected. Radio emission of some identified objects seems to have a magnetic nature and be produced by gyrosynchrotron mechanism. In particular, one of the sources shows a radio radiation circularly polarized; two other stars have a radiation strongly variable probably due to magnetic eruptions more important than those detected in X radiation. More generally, radio observations select probably a specific population of young stars characterized by magnetic field presence extended on several stellar radii and by absence of dense circumstellar environment. Spatial distribution of these objects suggest, they are younger than most of the pre-main sequence stars [fr

LSPM J1314+1320: An Oversized Magnetic Star with Constraints on the Radio Emission Mechanism

Energy Technology Data Exchange (ETDEWEB)

MacDonald, James; Mullan, D. J. [Dept. Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)

2017-07-10

LSPM J1314+1320 (=NLTT 33370) is a binary star system consisting of two nearly identical pre-main-sequence stars of spectral type M7. The system is remarkable among ultracool dwarfs for being the most luminous radio emitter over the widest frequency range. Masses and luminosities are at first sight consistent with the system being coeval at age ∼80 Myr according to standard (nonmagnetic) evolutionary models. However, these models predict an average effective temperature of ∼2950 K, which is 180 K hotter than the empirical value. Thus, the empirical radii are oversized relative to the standard models by ≈13%. We demonstrate that magnetic stellar models can quantitatively account for the oversizing. As a check on our models, we note that the radio emission limits the surface magnetic field strengths: the limits depend on identifying the radio emission mechanism. We find that the field strengths required by our magnetic models are too strong to be consistent with gyrosynchrotron emission but are consistent with electron cyclotron maser emission.

Interplanetary radio storms. 2: Emission levels and solar wind speed in the range 0.05-0.8 AU

Science.gov (United States)

Bougeret, J. L.; Fainberg, J.; Stone, R. G.

1982-01-01

Storms of interplanetary type III radio bursts (IP storms) are commonly observed in the interplanetry medium by the ISEE-3 radio instrument. This instrument has the capability of accurately determining the arrival direction of the radio emission. At each observing frequency, the storm radio sources are tracked as they cross the line-of-sight to the Sun. Usng a simple model, the emission levels are determined at a number of radio frequencies for four separate storms. The IP storm radiation is found to occur in regions of enhanced density at levels of 0.05 to 0.8 AU. The density in these enhancements falls off faster than R(-2). The solar wind speed in the storm region is also measured. The analysis is consistent with steady conditions in the storm region during a few days around the central meridian passage of the storm. The comparison with average in situ density measurements compiled from the HELIOS 1-2 observations favors type III storm burst radio emission at the harmonic of the local plasma frequency.

LOOKING FOR A PULSE: A SEARCH FOR ROTATIONALLY MODULATED RADIO EMISSION FROM THE HOT JUPITER, {tau} BOOeTIS b

Energy Technology Data Exchange (ETDEWEB)

Hallinan, G.; Bourke, S. [Cahill Center for Astrophysics, California Institute of Technology, 1200 E. California Blvd., MC 249-17, Pasadena, CA 91125 (United States); Sirothia, S. K.; Ishwara-Chandra, C. H. [National Centre for Radio Astrophysics, TIFR, Post Bag 3, Pune University Campus, Pune 411007 (India); Antonova, A. [Department of Astronomy, St. Kliment Ohridski University of Sofia, 5 James Bourchier Blvd., 1164 Sofia (Bulgaria); Doyle, J. G. [Armagh Observatory, College Hill, Armagh BT61 9DG (United Kingdom); Hartman, J. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Golden, A. [Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461 (United States)

2013-01-01

Hot Jupiters have been proposed as a likely population of low-frequency radio sources due to electron cyclotron maser emission of similar nature to that detected from the auroral regions of magnetized solar system planets. Such emission will likely be confined to specific ranges of orbital/rotational phase due to a narrowly beamed radiation pattern. We report on GMRT 150 MHz radio observations of the hot Jupiter {tau} Booetis b, consisting of 40 hr carefully scheduled to maximize coverage of the planet's 79.5 hr orbital/rotational period in an effort to detect such rotationally modulated emission. The resulting image is the deepest yet published at these frequencies and leads to a 3{sigma} upper limit on the flux density from the planet of 1.2 mJy, two orders of magnitude lower than predictions derived from scaling laws based on solar system planetary radio emission. This represents the most stringent upper limits for both quiescent and rotationally modulated radio emission from a hot Jupiter yet achieved and suggests that either (1) the magnetic dipole moment of {tau} Booetis b is insufficient to generate the surface field strengths of >50 G required for detection at 150 MHz or (2) Earth lies outside the beaming pattern of the radio emission from the planet.

Radio emission from pre-main-sequence stars in Corona Australis

International Nuclear Information System (INIS)

Brown, A.

1987-01-01

The central region of the Corona Australis molecular cloud surrounding the stars R and TY CrA has been studied using the VLA at 6 cm. Eleven radio sources are detected including five associated with pre-main-sequence objects. The most striking is associated with the near-IR source IRS 7 and shows a complex structure comprising two strong pointlike sources positioned either side of the deeply embedded IR source and two extended lobes of radio emission. The IRS 7 radio source appears to be similar to that associated with Lynds 1551 IRS 5 but has a considerably larger angular size. The other detected sources include the massive pre-main-sequence star TY CrA, the near-IR sources IRS 1 and IRS 5, and the Herbig-Haro object HH 101. The stars R and T CrA were not detected. 35 references

VARIABLE AND POLARIZED RADIO EMISSION FROM THE T6 BROWN DWARF WISEP J112254.73+255021.5

Energy Technology Data Exchange (ETDEWEB)

Williams, P. K. G.; Berger, E. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Gizis, J. E., E-mail: pwilliams@cfa.harvard.edu [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)

2017-01-10

Route and Wolszczan recently detected five radio bursts from the T6 dwarf WISEP J112254.73+255021.5 and used the timing of these events to propose that this object rotates with an ultra-short period of ∼17.3 minutes. We conducted follow-up observations with the Very Large Array and Gemini-North but found no evidence for this periodicity. We do, however, observe variable, highly circularly polarized radio emission. Assuming that the radio emission of this T dwarf is periodically variable on ∼hour timescales, like other radio-active ultracool dwarfs, we infer a likely period of 116 minutes. However, our observation lasted only 162 minutes and so more data are needed to test this hypothesis. The handedness of the circular polarization switches twice and there is no evidence for any unpolarized emission component, the first time such a phenomenology has been observed in radio studies of very low-mass stars and brown dwarfs. We suggest that the object’s magnetic dipole axis may be highly misaligned relative to its rotation axis.

Characterising the VHE diffuse emission in the central 200 parsecs of our Galaxy with H.E.S.S.

Science.gov (United States)

H.E.S.S. Collaboration; Abdalla, H.; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Andersson, T.; Angüner, E. O.; Arakawa, M.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bonnefoy, S.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Büchele, M.; Bulik, T.; Capasso, M.; Carr, J.; Casanova, S.; Cerruti, M.; Chakraborty, N.; Chaves, R. C. G.; Chen, A.; Chevalier, J.; Coffaro, M.; Colafrancesco, S.; Cologna, G.; Condon, B.; Conrad, J.; Cui, Y.; Davids, I. D.; Decock, J.; Degrange, B.; Deil, C.; Devin, J.; deWilt, P.; Dirson, L.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O.'C.; Dutson, K.; Dyks, J.; Edwards, T.; Egberts, K.; Eger, P.; Ernenwein, J.-P.; Eschbach, S.; Farnier, C.; Fegan, S.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Funk, S.; Füßling, M.; Gabici, S.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Goyal, A.; Grondin, M.-H.; Hahn, J.; Haupt, M.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holch, T. L.; Holler, M.; Horns, D.; Ivascenko, A.; Iwasaki, H.; Jacholkowska, A.; Jamrozy, M.; Janiak, M.; Jankowsky, D.; Jankowsky, F.; Jingo, M.; Jogler, T.; Jouvin, L.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katsuragawa, M.; Katz, U.; Kerszberg, D.; Khangulyan, D.; Khélifi, B.; King, J.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Kraus, M.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lees, J.-P.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Leser, E.; Lohse, T.; Lorentz, M.; Liu, R.; López-Coto, R.; Lypova, I.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Morå, K.; Moulin, E.; Murach, T.; Nakashima, S.; de Naurois, M.; Niederwanger, F.; Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Ohm, S.; Ostrowski, M.; Oya, I.; Padovani, M.; Panter, M.; Parsons, R. D.; Pekeur, N. W.; Pelletier, G.; Perennes, C.; Petrucci, P.-O.; Peyaud, B.; Piel, Q.; Pita, S.; Poon, H.; Prokhorov, D.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Rauth, R.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Richter, S.; Rieger, F.; Romoli, C.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Saito, S.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwemmer, S.; Seglar-Arroyo, M.; Settimo, M.; Seyffert, A. S.; Shafi, N.; Shilon, I.; Simoni, R.; Sol, H.; Spanier, F.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stycz, K.; Sushch, I.; Takahashi, T.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tibaldo, L.; Tiziani, D.; Tluczykont, M.; Trichard, C.; Tsuji, N.; Tuffs, R.; Uchiyama, Y.; van der Walt, D. J.; van Eldik, C.; van Rensburg, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zaborov, D.; Zacharias, M.; Zanin, R.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Żywucka, N.

2018-04-01

The diffuse very high-energy (VHE; >100 GeV) γ-ray emission observed in the central 200 pc of the Milky Way by H.E.S.S. was found to follow dense matter distribution in the central molecular zone (CMZ) up to a longitudinal distance of about 130 pc to the Galactic centre (GC), where the flux rapidly decreases. This was initially interpreted as the result of a burst-like injection of energetic particles 104 yr ago, but a recent more sensitive H.E.S.S. analysis revealed that the cosmic-ray (CR) density profile drops with the distance to the centre, making data compatible with a steady cosmic PeVatron at the GC. In this paper, we extend this analysis to obtain, for the first time, a detailed characterisation of the correlation with matter and to search for additional features and individual γ-ray sources in the inner 200 pc. Taking advantage of 250 h of H.E.S.S. data and improved analysis techniques, we perform a detailed morphology study of the diffuse VHE emission observed from the GC ridge and reconstruct its total spectrum. To test the various contributions to the total γ-ray emission, we used an iterative 2D maximum-likelihood approach that allows us to build a phenomenological model of the emission by summing a number of different spatial components. We show that the emission correlated with dense matter covers the full CMZ and that its flux is about half the total diffuse emission flux. We also detect some emission at higher latitude that is likely produced by hadronic collisions of CRs in less dense regions of the GC interstellar medium. We detect an additional emission component centred on the GC and extending over about 15 pc that is consistent with the existence of a strong CR density gradient and confirms the presence of a CR accelerator at the very centre of our Galaxy. We show that the spectrum of full ridge diffuse emission is compatible with that previously derived from the central regions, suggesting that a single population of particles fills the

Generation of auroral hectometer radio emission at the laser cyclotron resonance (ωp≥ωH)

International Nuclear Information System (INIS)

Vlasov, V.G.

1992-01-01

Generation of auroral hectometer (AHR) and kilometer (AKR) radio emission at a maser cyclotron resonance (MCR) in a relatively dense plasma (ω p ≥ω H ) is theoretically studied. The conclusion is made that availability of two-dimensional small-scale inhomogeneity of plasma density is the basic condition for the AHR generation at the MCR by auroral electron beams. The small-scale inhomogeneity of the auroral plasma, measured on satelites, meets by its parameters the conditions for the generation of auroral radio emission

3D-CFD analysis of diffusion and emission of VOCs in a FLEC cavity.

Science.gov (United States)

Zhu, Q; Kato, S; Murakami, S; Ito, K

2007-06-01

This study is performed as a part of research that examines the emission and diffusion characteristics of volatile organic compounds (VOCs) from indoor building materials. In this paper, the flow field and the emission field of VOCs from the surface of building materials in a Field and Laboratory Emission Cell (FLEC) cavity are examined by 3D Computational Fluid Dynamics (CFD) analysis. The flow field within the FLEC cavity is laminar. With a total flow of 250 ml/min, the air velocity near the test material surface ranges from 0.1 to 4.5 cm/s. Three types of emission from building materials are studied here: (i) emission phenomena controlled by internal diffusion, (ii) emission phenomena controlled by external diffusion, and (iii) emission phenomena controlled by mixed diffusion (internal + external diffusion). In the case of internal diffusion material, with respect to the concentration distribution in the cavity, the local VOC emission rate becomes uniform and the FLEC works well. However, in the case of evaporation type (external diffusion) material, or mixed type materials (internal + external diffusion) when the resistance to transporting VOCs in the material is small, the FLEC is not suitable for emission testing because of the thin FLEC cavity. In this case, the mean emission rate is restricted to a small value, since the VOC concentration in the cavity rises to the same value as the surface concentration through molecular diffusion within the thin cavity, and the concentration gradient normal to the surface becomes small. The diffusion field and emission rate depend on the cavity concentration and on the Loading Factor. That is, when the testing material surface in the cavity is partially sealed to decrease the Loading Factor, the emission rate become higher with the decrease in the exposed area of the testing material. The flow field and diffusion field within the FLEC cavity are investigated by CFD method. After presenting a summary of the velocity

THE UBIQUITOUS RADIO CONTINUUM EMISSION FROM THE MOST MASSIVE EARLY-TYPE GALAXIES

International Nuclear Information System (INIS)

Brown, Michael J. I.; Jannuzi, Buell T.; Floyd, David J. E.; Mould, Jeremy R.

2011-01-01

We have measured the radio continuum emission of 396 early-type galaxies brighter than K = 9, using 1.4 GHz imagery from the NRAO Very Large Array Sky Survey, Green Bank 300 ft Telescope, and 64 m Parkes Radio Telescope. For M K K < -25.5 early-type galaxies are greater than zero in all cases. It is thus highly likely that the most massive galaxies always host an active galactic nucleus or have recently undergone star formation.

EFFECTS OF ALFVEN WAVES ON ELECTRON CYCLOTRON MASER EMISSION IN CORONAL LOOPS AND SOLAR TYPE I RADIO STORMS

Energy Technology Data Exchange (ETDEWEB)

Zhao, G. Q.; Chen, L.; Wu, D. J. [Purple Mountain Observatory, CAS, Nanjing 210008 (China); Yan, Y. H., E-mail: djwu@pmo.ac.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, CAS, Beijing 100012 (China)

2013-06-10

Solar type I radio storms are long-lived radio emissions from the solar atmosphere. It is believed that these type I storms are produced by energetic electrons trapped within a closed magnetic structure and are characterized by a high ordinary (O) mode polarization. However, the microphysical nature of these emissions is still an open problem. Recently, Wu et al. found that Alfven waves (AWs) can significantly influence the basic physics of wave-particle interactions by modifying the resonant condition. Taking the effects of AWs into account, this work investigates electron cyclotron maser emission driven by power-law energetic electrons with a low-energy cutoff distribution, which are trapped in coronal loops by closed solar magnetic fields. The results show that the emission is dominated by the O mode. It is proposed that this O mode emission may possibly be responsible for solar type I radio storms.

Fermi-LAT and Suzaku Observations of the Radio Galaxy Centaurus B

International Nuclear Information System (INIS)

Katsuta, Junichiro

2012-01-01

CentaurusB is a nearby radio galaxy positioned in the Southern hemisphere close to the Galactic plane. Here we present a detailed analysis of about 43 months accumulation of Fermi-LAT data and of newly acquired Suzaku X-ray data for Centaurus B. The source is detected at GeV photon energies, although we cannot completely exclude the possibility that it is an artifact due to incorrect modeling of the bright Galactic diffuse emission in the region. The LAT image provides a weak hint of a spatial extension of the γ rays along the radio lobes, which is consistent with the lack of source variability in the GeV range. We note that the extension cannot be established statistically due to the low number of the photons. Surprisingly, we do not detect any diffuse emission of the lobes at X-ray frequencies, with the provided upper limit only marginally consistent with the previously claimed ASCA flux. The broad-band modeling shows that the observed γ-ray flux of the source may be produced within the lobes, if the diffuse non-thermal X-ray emission component is not significantly below the derived Suzaku upper limit. This association would imply that efficient in-situ acceleration of the ultrarelativistic particles is occurring and that the lobes are dominated by the pressure from the relativistic particles. However, if the diffuse X-ray emission is much below the Suzaku upper limits, the observed γ-ray flux is not likely to be produced within the lobes, but instead within the unresolved core of Centaurus B. In this case, the extended lobes could be dominated by the pressure of the magnetic field.

Fermi-LAT and Suzaku Observations of the Radio Galaxy Centaurus B

Energy Technology Data Exchange (ETDEWEB)

Katsuta, Junichiro; /Stanford U., HEPL /KIPAC, Menlo Park; Tanaka, Y.T.; /Hiroshima U.; Stawarz, L.; /JAXA, Sagamihara /Jagiellonian U., Astron. Observ.; O' Sullivan, S.P.; /Australia, CSIRO, Epping; Cheung, C.C.; /NAS, Washington, D.C.; Kataoka, J.; /Waseda U., RISE; Funk, S.; /Stanford U., HEPL /KIPAC, Menlo Park; Yuasa, T.; Odaka, H.; Takahashi, T.; /JAXA, Sagamihara; Svoboda, J.; /European Space Agency

2012-08-17

CentaurusB is a nearby radio galaxy positioned in the Southern hemisphere close to the Galactic plane. Here we present a detailed analysis of about 43 months accumulation of Fermi-LAT data and of newly acquired Suzaku X-ray data for Centaurus B. The source is detected at GeV photon energies, although we cannot completely exclude the possibility that it is an artifact due to incorrect modeling of the bright Galactic diffuse emission in the region. The LAT image provides a weak hint of a spatial extension of the {gamma} rays along the radio lobes, which is consistent with the lack of source variability in the GeV range. We note that the extension cannot be established statistically due to the low number of the photons. Surprisingly, we do not detect any diffuse emission of the lobes at X-ray frequencies, with the provided upper limit only marginally consistent with the previously claimed ASCA flux. The broad-band modeling shows that the observed {gamma}-ray flux of the source may be produced within the lobes, if the diffuse non-thermal X-ray emission component is not significantly below the derived Suzaku upper limit. This association would imply that efficient in-situ acceleration of the ultrarelativistic particles is occurring and that the lobes are dominated by the pressure from the relativistic particles. However, if the diffuse X-ray emission is much below the Suzaku upper limits, the observed {gamma}-ray flux is not likely to be produced within the lobes, but instead within the unresolved core of Centaurus B. In this case, the extended lobes could be dominated by the pressure of the magnetic field.

Effective Spectral Indices of Core and Extended Emissions for Radio ...

Indian Academy of Sciences (India)

Effective Spectral Indices of Core and Extended Emissions for Radio Sources. R. S. Yang1,∗, J. H. Yang1,2 & J. J. Nie1. 1Department of Physics and Electronics Science, Hunan University of Arts and Science,. Changde 415000, China. 2Centre for Astrophysics, Guangzhou University, Guangzhou 510006, China. ∗ e-mail: ...

On a possible mechanism of quasi periodic pulses of the quiet Sun decametric radio emission

International Nuclear Information System (INIS)

Levin, B.N.; Snegireva, S.D.

1983-01-01

The observed fluctuations of the quiet Sun decametric radio emission are interpreted on the basis of the plasma mechanism of generation. These fluctuations may be caused by modulation of the optical depth of the radio source due to propagation of the sound wave packet through the corona

AN ANALYSIS OF INTERPLANETARY SOLAR RADIO EMISSIONS ASSOCIATED WITH A CORONAL MASS EJECTION

Energy Technology Data Exchange (ETDEWEB)

Krupar, V.; Eastwood, J. P. [The Blackett Laboratory, Imperial College London, London (United Kingdom); Kruparova, O.; Santolik, O.; Soucek, J., E-mail: v.krupar@imperial.ac.uk, E-mail: jonathan.eastwood@imperial.ac.uk, E-mail: ok@ufa.cas.cz, E-mail: os@ufa.cas.cz, E-mail: soucek@ufa.cas.cz [Institute of Atmospheric Physics CAS, Prague (Czech Republic); and others

2016-05-20

Coronal mass ejections (CMEs) are large-scale eruptions of magnetized plasma that may cause severe geomagnetic storms if Earth directed. Here, we report a rare instance with comprehensive in situ and remote sensing observations of a CME combining white-light, radio, and plasma measurements from four different vantage points. For the first time, we have successfully applied a radio direction-finding technique to an interplanetary type II burst detected by two identical widely separated radio receivers. The derived locations of the type II and type III bursts are in general agreement with the white-light CME reconstruction. We find that the radio emission arises from the flanks of the CME and are most likely associated with the CME-driven shock. Our work demonstrates the complementarity between radio triangulation and 3D reconstruction techniques for space weather applications.

Why is observable radio recombination line emission from galactic HII regions always close to LTE

International Nuclear Information System (INIS)

Shaver, P.A.

1980-01-01

There is no evidence for significant deviations from LTE in single-dish observations of radio recombination line emission from galactic HII regions. This is in agreement with the known properties of HII regions, particularly their density variations and limited range of excitation parameters; the optimum configuration for strong observable non-LTE effects, low electron density and high emission measure, simply does not exist in galactic HII regions, and the observed lines are emitted under near-LTE conditions. Models of the Orion Nebulae and NGC 6604 are presented which fit all available data and show only weak stimulated emission. It is concluded that reliable electron temperatures can indeed be obtained from straightforward analysis of appropriate radio recombination lines. (orig.)

Discovery of Diffuse Hard X-ray Emission associated with Jupiter

Science.gov (United States)

Ezoe, Y.; Miyoshi, Y.; Ishikawa, K.; Ohashi, T.; Terada, N.; Uchiyama, Y.; Negoro, H.

2009-12-01

Our discovery of diffuse hard (1-5 keV) X-ray emission around Jupiter is reported. Recent Chandra and XMM-Newton observations revealed several types of X-rays in the vicinity of Jupiter such as auroral and disk emission from Jupiter and faint diffuse X-rays from the Io Plasma Torus (see Bhardwaj et al. 2007 for review). To investigate possible diffuse hard X-ray emission around Jupiter with the highest sensitivity, we conducted data analysis of Suzaku XIS observations of Jupiter on Feb 2006. After removing satellite and planetary orbital motions, we detected a significant diffuse X-ray emission extending to ~6 x 3 arcmin with the 1-5 keV X-ray luminosity of ~3e15 erg/s. The emitting region very well coincided with the Jupiter's radiation belts. The 1-5 keV X-ray spectrum was represented by a simple power law model with a photon index of 1.4. Such a flat continuum strongly suggests non-thermal origin. Although such an emission can be originated from multiple background point sources, its possibility is quite low. We hence examined three mechanisms, assuming that the emission is truly diffuse: bremsstrahlung by keV electrons, synchrotron emission by TeV electrons, and inverse Compton scattering of solar photons by MeV electrons. The former two can be rejected because of the X-ray spectral shape and implausible existence of TeV electrons around Jupiter, respectively. The last possibility was found to be possible because tens MeV electrons, which have been confirmed in inner radiation belts (Bolton et al. 2002), can kick solar photons to the keV energy range and provide a simple power-law continuum. We estimated an average electron density from the X-ray luminosity assuming the oblate spheroid shaped emitting region with 8 x 8 x 4 Jovian radii. The necessary density was 0.02 1/cm3 for 50 MeV electrons. Hence, our results may suggest a new particle acceleration phenomenon around Jupiter.

Variations of Synchrotron Radio Emissions from Jupiter's Inner Radiation Belt

Science.gov (United States)

Lou, Y.-Q.

2017-09-01

Variations of Synchrotron Radio Emissions from Jupiter's Inner Radiation Belt Yu-Qing Lou* Physics Department, Tsinghua Centre for Astrophysics (THCA), Tsinghua-National Astronomical Observatories of China (NAOC) joint Research Centre for Astrophysics, Tsinghua University, Beijing 100084, China We describe the basic phenommenology of quasi-periodic 40 minute (QP-40) polar burst activities of Jupiter and their close correlation with the solar wind speed variations at the Jovian magnetosphere. Physically, relativistic electrons of QP-40 bursts most likely come from the circumpolar regions of the inner radiation belt (IRB) which gives off intense synchroton radio emissions in a wide wavelength range. Such relativistic electron bursts also give rise to beamed low-frequency radio bursts along polar magnetic field lines with distinct polarizations from Jupiter's two polar regions. Jovian aurora activities are expected to be also affected by such QP-40 burst activities. We present evidence of short-term (typical timescales shorter than an hour) variabilities of the IRB at 6cm wavelength and describe recent joint radio telescope observation campaign to monitor Jupiter in coordination with JUNO spacecraft. Except for low-frequency polarization features, we anticipate JUNO to detect QP-40 activities from both polar regions during the arrival of high-speed solar wind with intermittency. References 1. Y.-Q. Lou, The Astrophysical Journal, 548, 460 (2001). 2. Y.-Q. Lou, and C. Zheng, Mon. Not. Roy. Astron. Soc. Letters, 344, L1 (2003). 3. Y.-Q. Lou, H. G. Song, Y.Y. Liu, and M. Yang, Mon. Not. Roy. Astron. Soc. Letters, 421, L62 (2012). 4. Y.-Q. Lou, Geophysical Research Letters, 23, 609 (1996). 5. Y.-Q. Lou, Journal of Geophysical Research, 99, 14747 (1994). 6. G. R. Gladstone, et al., Nature, 415, 1000 (2002).

Correlation of optical emission and turbulent length scale in a coaxial jet diffusion flame

OpenAIRE

松山, 新吾; Matsuyama, Shingo

2014-01-01

This article investigates the correlation between optical emission and turbulent length scale in a coaxial jet diffusion flame. To simulate the H2O emission from an H2/O2 diffusion flame, radiative transfer is calculated on flame data obtained by numerical simulation. H2O emission characteristics are examined for a one-dimensional opposed-flow diffusion flame. The results indicate that H2O emission intensity is linearly dependent on flame thickness. The simulation of H2O emission is then exte...

MODELING THE RADIO EMISSION FROM Cyg OB2 NO. 5: A QUADRUPLE SYSTEM?

International Nuclear Information System (INIS)

Kennedy, M.; Dougherty, S. M.; Fink, A.; Williams, P. M.

2010-01-01

Fifty observations at frequencies between 1.4 GHz and 43 GHz of the 6.6 day O6.5-7+O5.5-6 binary Cyg OB2 No. 5 using the Very Large Array over 20 years are re-examined. The aim is to determine the location and character of the previously detected variable radio emission. The radio emission from the system consists of a primary component that is associated with the binary, and a non-thermal source (NE), 0.''8 to the NE of the binary that has been ascribed to a wind-collision region (WCR) between the stellar winds of the binary and that of a B-type star (Star D) to the NE. Previous studies have not accounted for the potential contribution of NE to the total radio emission, most especially in observations where the primary and NE sources are not resolved as separate sources. NE shows no evidence of variation in 23 epochs where it is resolved separately from the primary radio component, demonstrating that the variable emission arises in the primary component. Since NE is non-variable, the radio flux from the primary can now be well determined for the first time, most especially in observations that do not resolve both the primary and NE components. The variable radio emission from the primary component has a period of 6.7 ± 0.3 years which is described by a simple model of a non-thermal source orbiting within the stellar wind envelope of the binary. Such a model implies the presence of a third, unresolved stellar companion (Star C) orbiting the 6.6 day binary with a period of 6.7 years and independent of Star D to the NE. The variable non-thermal emission arises from either a WCR between Star C and the binary system, or possibly from Star C directly. The model gives a mass-loss rate of 3.4 x 10 -5 M sun yr -1 for Cyg OB2 No. 5, unusually high for an Of supergiant and comparable to that of WR stars, and consistent with an unusually strong He I 1.083 μm emission line, also redolent of WR stars. An examination of radial velocity observations available from the

Workshop on Radio Recombination Lines

CERN Document Server

1980-01-01

Since their first detection 15 years ago, radio recombination lines from several elements have been observed in a wide variety of objects including HII regions, planetary nebulae, molecular clouds, the diffuse interstellar medium, and recently, other galaxies. The observations span almost the entire range from 0.1 to 100 GHz, and employ both single­ djsh and aperture synthesis techniques. The theory of radio recombination lines has also advanced strongly, to the point where it is perhaps one of the best-understood in astro­ physics. In a parallel development, it has become possible over the last decade to study these same highly-excited atoms in the laboratory; this work provides further confirmation of the theoretical framework. However there has been continuing controversy over the astrophysical interpre­ tation of radio recombination line observations, especially regarding the role of stimulated emission. A workshop was held in Ottawa on 24-25 August, 1979, bringing together many of the active scientist...

The Origin of the Infrared Emission in Radio Galaxies : III. Analysis of 3CRR Objects

NARCIS (Netherlands)

Dicken, D.; Tadhunter, C.; Axon, D.; Robinson, A.; Morganti, R.; Kharb, P.

2010-01-01

We present Spitzer photometric data for a complete sample of 19 low-redshift (z <0.1) 3CRR radio galaxies as part of our efforts to understand the origin of the prodigious mid-to far-infrared (MFIR) emission from radio-loud active galactic nuclei (AGNs). Our results show a correlation between AGN

Gnevyshev peaks in solar radio emissions at different frequencies

Directory of Open Access Journals (Sweden)

R. P. Kane

2009-04-01

Full Text Available Sunspots have a major 11-year cycle, but the years near the sunspot maximum show two or more peaks called GP (Gnevyshev Peaks. In this communication, it was examined whether these peaks in sunspots are reflected in other parameters such as Lyman-α (the chromospheric emission 121.6 nm, radio emissions 242–15 400 MHz emanating from altitude levels 2000–12 000 km, the low latitude (+45° to −45° solar open magnetic flux and the coronal green line emission (Fe XIV, 530.3 nm. In the different solar cycles 20–23, the similarity extended at least upto the level of 609 MHz, but in cycle 22, the highest level was of 242 MHz. The extension to the higher level in cycle 22 does not seem to be related to the cycle strength Rz(max, or to the cycle length.

Strongly lensed neutral hydrogen emission: detection predictions with current and future radio interferometers

Science.gov (United States)

Deane, R. P.; Obreschkow, D.; Heywood, I.

2015-09-01

Strong gravitational lensing provides some of the deepest views of the Universe, enabling studies of high-redshift galaxies only possible with next-generation facilities without the lensing phenomenon. To date, 21-cm radio emission from neutral hydrogen has only been detected directly out to z ˜ 0.2, limited by the sensitivity and instantaneous bandwidth of current radio telescopes. We discuss how current and future radio interferometers such as the Square Kilometre Array (SKA) will detect lensed H I emission in individual galaxies at high redshift. Our calculations rely on a semi-analytic galaxy simulation with realistic H I discs (by size, density profile and rotation), in a cosmological context, combined with general relativistic ray tracing. Wide-field, blind H I surveys with the SKA are predicted to be efficient at discovering lensed H I systems, increasingly so at z ≳ 2. This will be enabled by the combination of the magnification boosts, the steepness of the H I luminosity function at the high-mass end, and the fact that the H I spectral line is relatively isolated in frequency. These surveys will simultaneously provide a new technique for foreground lens selection and yield the highest redshift H I emission detections. More near term (and existing) cm-wave facilities will push the high-redshift H I envelope through targeted surveys of known lenses.

Investigation of the dynamics of HF plasma turbulence by means of artificial ionospheric radio emission

International Nuclear Information System (INIS)

Sergeev, E.N.; Boiko, G.N.; Frolov, V.L.

1994-01-01

The results of measurements of the growth and decay characteristics of artificial ionospheric radio emission and their dependence on the level of low-frequency artificial turbulence, time of day, and pump-wave frequency are presented. A time delay of the onset of the exponential nature of the decay process is detected, and its characteristics are studied. It is shown that the effect is determined by nonlinear pumping over the spectrum of high-frequency plasma turbulence. The experimental results demonstrate the possibilities of using artificial radio emission to study the properties of high-frequency plasma turbulence. Areas of future research are discussed

On the Reflection in the Solar Radio Emission of Processes in the Chromosphere and the lower Corona preceded CMEs Registration

Science.gov (United States)

Durasova, M. S.; Tikhomirov, Yu. V.; Fridman, V. M.; Sheiner, O. A.

The phenomena preceding the Coronal Mass Ejections (CMEs) and observed in the radio-frequency band represent a lot of sporadic components of the emission, that cover the wide frequency range. The study of these phenomena composes the new, prevailing for the last ten years direction. This is caused by the fact that solar radioastronomy possesses the developed network of observant tools, by the sensitive methods of observations. It makes possible in a number of cases to obtain information from the layers of solar atmosphere, inaccessible for the studies by other methods of observations. The purpose of this work is analysis of information about the CMEs preceding radio-events and their dynamics in the centimeter and decimeter radio emission in 1998. We use the data of the worldwide network of solar observatories in the radio-frequency band, the data about the CMEs phenomena and the characteristics are taken from Internet: http://sdaw.gsfc.nasa.gov./CME_list}. From great number of the CMEs we select only such, before which there were no more recorded events in the time interval of 8 hours, and before which sporadic radio emission was observed on 2-hours interval. The selection of this interval was caused by available study about the mean lifetime of precursors before CMEs and powerful flares, as a rule, accompanying CMEs, in the optical, X-ray and radio emissions. It constitutes, on the average, about 30 min. The total volume of data composed 68 analyzed events of CMEs in 1998. The analysis of the spectral- temporary characteristics of sporadic radio emission in the dependence on the CMEs parameters is carried out. The nature of processes at the stage of formation and initial propagation of CMEs, such as floating up of new magnetic fluxes, the development of instabilities, the characteristic scales of phenomena, that have an effect upon the observed radio emission is analyzed. The work is carried out with the support of Russian Fund of Basic Research (grant 03

Managing the diffusion of low emission vehicles

NARCIS (Netherlands)

Vooren, A. van der; Alkemade, F.

2012-01-01

There is significant uncertainty among technology providers, governments, and consumers about which technology will be the vehicle technology of the future. Governments try to stimulate the diffusion of low emission vehicles with diverse policy measures such as purchase price subsidies. However, the

Radio stars

International Nuclear Information System (INIS)

Hjellming, R.M.

1976-01-01

Any discussion of the radio emission from stars should begin by emphasizing certain unique problems. First of all, one must clarify a semantic confusion introduced into radio astronomy in the late 1950's when most new radio sources were described as radio stars. All of these early 'radio stars' were eventually identified with other galactic and extra-galactic objects. The study of true radio stars, where the radio emission is produced in the atmosphere of a star, began only in the 1960's. Most of the work on the subject has, in fact, been carried out in only the last few years. Because the real information about radio stars is quite new, it is not surprising that major aspects of the subject are not at all understood. For this reason this paper is organized mainly around three questions: what is the available observational information; what physical processes seem to be involved; and what working hypotheses look potentially fruitful. (Auth.)

DISCOVERY OF A GIANT RADIO HALO IN A NEW PLANCK GALAXY CLUSTER PLCKG171.9-40.7

Energy Technology Data Exchange (ETDEWEB)

Giacintucci, Simona [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Kale, Ruta; Venturi, Tiziana [INAF-Istituto di Radioastronomia, via Gobetti 101, I-40129 Bologna (Italy); Wik, Daniel R.; Markevitch, Maxim, E-mail: simona@astro.umd.edu [Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2013-03-20

We report the discovery of a giant radio halo in a new, hot, X-ray luminous galaxy cluster recently found by Planck, PLCKG171.9-40.7. The radio halo was found using Giant Metrewave Radio Telescope observations at 235 MHz and 610 MHz, and in the 1.4 GHz data from an NRAO Very Large Array Sky Survey pointing that we have reanalyzed. The diffuse radio emission is coincident with the cluster X-ray emission, and has an extent of {approx}1 Mpc and a radio power of {approx}5 Multiplication-Sign 10{sup 24} W Hz{sup -1} at 1.4 GHz. Its integrated radio spectrum has a slope of {alpha} Almost-Equal-To 1.8 between 235 MHz and 1.4 GHz, steeper than that of a typical giant halo. The analysis of the archival XMM-Newton X-ray data shows that the cluster is hot ({approx}10 keV) and disturbed, consistent with X-ray-selected clusters hosting radio halos. This is the first giant radio halo discovered in one of the new clusters found by Planck.

Offset, tilted dipole models of Uranian smooth high-frequency radio emission

International Nuclear Information System (INIS)

Schweitzer, A.E.; Romig, J.H.; Evans, D.R.; Sawyer, C.B.; Warwick, J.W.

1990-01-01

During the Voyager 2 encounter with Uranus in January 1986, the Planetary Radio Astronomy (PRA) experiment detected a complex pattern of radio emissions. Two types of emissions were seen: smooth and bursty. The smooth emission has been divided into smooth high-frequency (SHF) and smooth low-frequency (SLF) components which are presumed to come from different sources because of their distinctly different characteristics. The SHF component is considered in this paper. The SHF emission has been modeled by many authors on OTD (offset, tilted dipole (Ness et al., 1986)) L shells ranging from 5 to 40. However, the bursts have been modeled at much higher L shells. The authors complete an OTD investigation of the SHF emission at high L shells within the range of the bursty source locations, and present a viable high L shell model. This model has fundamentally the same longitudinally symmetric net emission pattern in space as the L shell 5 model presented in Romig et al. (1987) and Barbosa (1988). However, they were unable to produce an acceptable model on intermediate L shells without restricting source longitude. They discuss the similarities and distinctions between their two models and the models of other authors. They believe that the high L shell model (and others similar to it) cannot account for the observed smoothness and periodicity of the SHF emissions because it has open field lines containing untrapped particles, which should produce more variable emission than that seen in the SHF data. Therefore, the authors prefer models at L shells less than 18, the boundary for closed field lines (Ness et al., 1986). They then discuss and contrast two models within this boundary: the L = 5 model and an L ∼ 12 model by Kaiser et al. (1987) and Farrell and Calvert (1989b). The main distinction between these two models is the longitudinal extent of the source location

Broad Line Radio Galaxies Observed with Fermi-LAT: The Origin of the GeV Gamma-Ray Emission

Energy Technology Data Exchange (ETDEWEB)

Kataoka, J.; /Waseda U., RISE; Stawarz, L.; /JAXA, Sagamihara /Jagiellonian U., Astron. Observ.; Takahashi, Y.; /Waseda U., RISE; Cheung, C.C.; /Natl. Acad. Sci. /Naval Research Lab, Wash., D.C.; Hayashida, M.; /SLAC /Stanford U., HEPL /KIPAC, Menlo Park; Grandi, P.; /Bologna Observ.; Burnett, T.H.; /Washington U., Seattle; Celotti, A.; /SISSA, Trieste; Fegan, S.J.; Fortin, P.; /Ecole Polytechnique; Maeda, K.; Nakamori, T.; /Waseda U., RISE; Taylor, G.B.; /New Mexico U.; Tosti, G.; /INFN, Perugia /Perugia U.; Digel, S.W.; /SLAC /Stanford U., HEPL /KIPAC, Menlo Park; McConville, W.; /NASA, Goddard /Maryland U.; Finke, J.; /Naval Research Lab, Wash., D.C.; D' Ammando, F.; /IASF, Palermo /INAF, Rome

2012-06-07

We report on a detailed investigation of the {gamma}-ray emission from 18 broad line radio galaxies (BLRGs) based on two years of Fermi Large Area Telescope (LAT) data. We confirm the previously reported detections of 3C 120 and 3C 111 in the GeV photon energy range; a detailed look at the temporal characteristics of the observed {gamma}-ray emission reveals in addition possible flux variability in both sources. No statistically significant {gamma}-ray detection of the other BLRGs was however found in the considered dataset. Though the sample size studied is small, what appears to differentiate 3C 111 and 3C 120 from the BLRGs not yet detected in {gamma}-rays is the particularly strong nuclear radio flux. This finding, together with the indications of the {gamma}-ray flux variability and a number of other arguments presented, indicate that the GeV emission of BLRGs is most likely dominated by the beamed radiation of relativistic jets observed at intermediate viewing angles. In this paper we also analyzed a comparison sample of high accretion-rate Seyfert 1 galaxies, which can be considered radio-quiet counterparts of BLRGs, and found none were detected in {gamma}-rays. A simple phenomenological hybrid model applied for the broad-band emission of the discussed radio-loud and radio-quiet type 1 active galaxies suggests that the relative contribution of the nuclear jets to the accreting matter is {ge} 1% on average for BLRGs, while {le} 0.1% for Seyfert 1 galaxies.

Propagation of Energetic Electrons from the Corona into Interplanetary Space and Type III Radio Emission. Planetary Radio Emissions| PLANETARY RADIO EMISSIONS VII 7|

OpenAIRE

Vocks, C.; Breitling, F.; Mann, G.

2011-01-01

During solar flares a large amount of electrons with energies greater than 20 keV is generated with a production rate of typically 1036 s-1. A part of them is able to propagate along open magnetic field lines through the corona into interplanetary space. During their travel they emit radio radiation which is observed as type III radio bursts in the frequency range from 100 MHz down to 10 kHz by the WAVES radio spectrometer aboard the spacecraft WIND, for instance. From the drift rates of thes...

Radio and X-ray properties of the source G29.37+0.1 linked to HESS J1844-030

Science.gov (United States)

Castelletti, G.; Supan, L.; Petriella, A.; Giacani, E.; Joshi, B. C.

2017-06-01

Aims: We report on the first detailed multiwavelength study of the radio source G29.37+0.1, which is an as-yet-unclassified object linked to the very-high-energy γ-emitting source HESS J1844-030. The origin of the multiwavelength emission toward G29.37+0.1 has not been clarified so far, leaving open the question about the physical relationship between these sources. Methods: Using observations carried out with the Giant Metrewave Radio Telescope (GMRT), we performed high-quality full-synthesis imaging at 610 MHz of the field containing G29.37+0.1. The obtained data, combined with observations at 1400 MHz from The Multi-Array Galactic Plane Imaging Survey (MAGPIS) were used to investigate in detail the properties of its radio emission. Additionally, we reprocessed archival data obtained with the XMM-Newton and Chandra observatories in order to get a multiwavelength view of this unusual source. Results: The radio source G29.37+0.1 mainly consists of a bright twisted structure, named the S-shaped feature. The high sensitivity of the new GMRT observations allowed the identification of potential lobes, jets, and a nuclear central region in the S-shaped morphology of G29.37+0.1. We also highlight the detection of diffuse and low surface brightness emission enveloping the brightest emitting regions. The brightest emission in G29.37+0.1 has a radio synchrotron spectral index α = 0.59 ± 0.09. Variations in the spectral behaviour are observed across the whole radio source with the flattest spectral features in the central nuclear and jets components (α 0.3). These results lead us to conclude that the brightest radio emission from G29.37+0.1 likely represents a newly recognized radio galaxy. The identification of optical and infrared counterparts to the emission arising from the core of G29.37+0.1 strengthens our interpretation of an extragalactic origin of the radio emission. We performed several tests to explain the physical mechanism responsible for the observed X

Fast hisslers: a form of magnetospheric radio emissions

International Nuclear Information System (INIS)

Siren, J.C.

1974-01-01

Auroral radio hiss bursts in the frequency range 2-18 kHz have been observed, with rise or turn-on-times of 20-50 ms, and fall or turn-off times of 20-80 ms. These time scales are too brief to reconcile with the Cerenkov radiation emission mechanism often proposed as the transducer that converts precipitating auroral electron kinetic energy into very-low-frequency radio wave energy. The auroral hiss bursts, called here ''fast hisslers,'' are observed to be ''dispersed,', that is, their arrival time at the receiving site is not simultaneous at all frequencies, but depends on frequency in a way that is consistent with propagation in the whistler mode of electromagnetic wave propagation. Since whistler mode wave propagation at these frequencies occurs only in the earth' magnetosphere, it is inferred that these fast hisslers are of magnetospheric origin. On the assumption that all the observed dispersion results from whistler mode dispersion at high latitudes, altitudes of origin of 1800 km to 30,000 km are calculated for these emissions. Fine details of some of the amplitude spectra of fast hisslers have been examined. Potential double layers have been investigated as a highly localized region of acceleration of the auroral electrons that are believed to be the source of energy of the fast hisslers. Evidence is strong that a plasma instability exists which rapidly converts electron kinetic energies into whistler-mode wave energy traveling in the same direction relative to the rest frame of the thermal magnetospheric plasma

Testing the Young Neutron Star Scenario with Persistent Radio Emission Associated with FRB 121102

International Nuclear Information System (INIS)

Kashiyama, Kazumi; Murase, Kohta

2017-01-01

Recently a repeating fast radio burst (FRB) 121102 has been confirmed to be an extragalactic event and a persistent radio counterpart has been identified. While other possibilities are not ruled out, the emission properties are broadly consistent with Murase et al. that theoretically proposed quasi-steady radio emission as a counterpart of both FRBs and pulsar-driven supernovae. Here, we constrain the model parameters of such a young neutron star scenario for FRB 121102. If the associated supernova has a conventional ejecta mass of M ej ≳ a few M ⊙ , a neutron star with an age of t age ∼ 10–100 years, an initial spin period of P i ≲ a few ms, and a dipole magnetic field of B dip ≲ a few × 10 13 G can be compatible with the observations. However, in this case, the magnetically powered scenario may be favored as an FRB energy source because of the efficiency problem in the rotation-powered scenario. On the other hand, if the associated supernova is an ultra-stripped one or the neutron star is born by the accretion-induced collapse with M ej ∼ 0.1 M ⊙ , a younger neutron star with t age ∼ 1–10 years can be the persistent radio source and might produce FRBs with the spin-down power. These possibilities can be distinguished by the decline rate of the quasi-steady radio counterpart.

Testing the Young Neutron Star Scenario with Persistent Radio Emission Associated with FRB 121102

Energy Technology Data Exchange (ETDEWEB)

Kashiyama, Kazumi [Department of Physics, The University of Tokyo, Bunkyo, Tokyo 113-0033 (Japan); Murase, Kohta [Department of Physics, The Pennsylvania State University, University Park, PA 16802 (United States)

2017-04-10

Recently a repeating fast radio burst (FRB) 121102 has been confirmed to be an extragalactic event and a persistent radio counterpart has been identified. While other possibilities are not ruled out, the emission properties are broadly consistent with Murase et al. that theoretically proposed quasi-steady radio emission as a counterpart of both FRBs and pulsar-driven supernovae. Here, we constrain the model parameters of such a young neutron star scenario for FRB 121102. If the associated supernova has a conventional ejecta mass of M {sub ej} ≳ a few M {sub ⊙}, a neutron star with an age of t {sub age} ∼ 10–100 years, an initial spin period of P{sub i} ≲ a few ms, and a dipole magnetic field of B {sub dip} ≲ a few × 10{sup 13} G can be compatible with the observations. However, in this case, the magnetically powered scenario may be favored as an FRB energy source because of the efficiency problem in the rotation-powered scenario. On the other hand, if the associated supernova is an ultra-stripped one or the neutron star is born by the accretion-induced collapse with M {sub ej} ∼ 0.1 M {sub ⊙}, a younger neutron star with t {sub age} ∼ 1–10 years can be the persistent radio source and might produce FRBs with the spin-down power. These possibilities can be distinguished by the decline rate of the quasi-steady radio counterpart.

On the Radio-emitting Particles of the Crab Nebula: Stochastic Acceleration Model

Energy Technology Data Exchange (ETDEWEB)

Tanaka, Shuta J. [Department of Physics, Faculty of Science and Engineering, Konan University, 8-9-1 Okamoto, Kobe, Hyogo 658-8501 (Japan); Asano, Katsuaki, E-mail: sjtanaka@center.konan-u.ac.jp [Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa City, Chiba, 277-8582 (Japan)

2017-06-01

The broadband emission of pulsar wind nebulae (PWNe) is well described by non-thermal emissions from accelerated electrons and positrons. However, the standard shock acceleration model of PWNe does not account for the hard spectrum in radio wavelengths. The origin of the radio-emitting particles is also important to determine the pair production efficiency in the pulsar magnetosphere. Here, we propose a possible resolution for the particle energy distribution in PWNe; the radio-emitting particles are not accelerated at the pulsar wind termination shock but are stochastically accelerated by turbulence inside PWNe. We upgrade our past one-zone spectral evolution model to include the energy diffusion, i.e., the stochastic acceleration, and apply the model to the Crab Nebula. A fairly simple form of the energy diffusion coefficient is assumed for this demonstrative study. For a particle injection to the stochastic acceleration process, we consider the continuous injection from the supernova ejecta or the impulsive injection associated with supernova explosion. The observed broadband spectrum and the decay of the radio flux are reproduced by tuning the amount of the particle injected to the stochastic acceleration process. The acceleration timescale and the duration of the acceleration are required to be a few decades and a few hundred years, respectively. Our results imply that some unveiled mechanisms, such as back reaction to the turbulence, are required to make the energies of stochastically and shock-accelerated particles comparable.

Building materials. VOC emissions, diffusion behaviour and implications from their use

International Nuclear Information System (INIS)

Katsoyiannis, Athanasios; Leva, Paolo; Barrero-Moreno, Josefa; Kotzias, Dimitrios

2012-01-01

Five cement- and five lime-based building materials were examined in an environmental chamber for their emissions of Volatile Organic Compounds (VOCs). Typical VOCs were below detection limits, whereas not routinely analysed VOCs, like neopentyl glycol (NPG), dominated the cement-based products emissions, where, after 72 h, it was found to occur, in levels as high as 1400 μg m −3 , accounting for up to 93% of total VOCs. The concentrations of NPG were not considerably changed between the 24 and 72 h of sampling. The permeability of building materials was assessed through experiments with a dual environmental chamber; it was shown that building materials facilitate the diffusion of chemicals through their pores, reaching equilibrium relatively fast (6 h). - Highlights: ► Neopentyl glycol is reported in emissions from building materials for the first time. ► Neopentyl glycol dominates the VOC emissions from cement-based building materials. ► A dual chamber was developed to control diffusion through building materials. ► Building materials facilitate diffusion of indoor air pollutants through their pores. - Neopentyl glycol was detected in high concentrations in emissions from building materials.

Soot emissions from turbulent diffusion flames burning simple alkane fuels

Energy Technology Data Exchange (ETDEWEB)

Canteenwalla, P.M.; Johnson, M.R. [Carleton Univ., Ottawa, ON (Canada). Dept. of Mechanical and Aerospace Engineering; Thomson, K.A.; Smallwood, G.J. [National Research Council of Canada, Ottawa, ON (Canada). Inst. for Chemical Process and Environmental Technology

2007-07-01

A classic problem in combustion involves measurement and prediction of soot emissions from turbulent diffusion flames. Very high-sensitivity measurements of particulate matter (PM) from very low-sooting diffusion flames burning methane and other simple alkane fuels have been enabled from recent advances in laser-induced incandescence (LII). In order to quantify soot emissions from a lab-scale turbulent diffusion flame burner, this paper presented a study that used LII to develop a sampling protocol. The purpose of the study was to develop an experimentally based model to predict PM emissions from flares used in industry using soot emissions from lab-scale flares. Quantitative results of mass of soot emitted per mass of fuel burned were presented across a range of flow conditions and fuels. The experiment used digital imaging to measure flame lengths and estimate flame residence times. Comparisons were also made between current measurements and results of previous researchers for soot in the overfire region. The study also considered the validity applicability of buoyancy based models for predicting and scaling soot emissions. The paper described the experimental setup including sampling system and flame length imaging. Background information on soot yield and a comparison of flame residence time definitions were provided. The results and discussion of results were also presented. It was concluded that the results highlighted the subjective nature of flame length measurements. 10 refs., 4 figs.

Jet-torus connection in radio galaxies. Relativistic hydrodynamics and synthetic emission

Science.gov (United States)

Fromm, C. M.; Perucho, M.; Porth, O.; Younsi, Z.; Ros, E.; Mizuno, Y.; Zensus, J. A.; Rezzolla, L.

2018-01-01

Context. High resolution very long baseline interferometry observations of active galactic nuclei have revealed asymmetric structures in the jets of radio galaxies. These asymmetric structures may be due to internal asymmetries in the jets or they may be induced by the different conditions in the surrounding ambient medium, including the obscuring torus, or a combination of the two. Aims: In this paper we investigate the influence of the ambient medium, including the obscuring torus, on the observed properties of jets from radio galaxies. Methods: We performed special-relativistic hydrodynamic (SRHD) simulations of over-pressured and pressure-matched jets using the special-relativistic hydrodynamics code Ratpenat, which is based on a second-order accurate finite-volume method and an approximate Riemann solver. Using a newly developed radiative transfer code to compute the electromagnetic radiation, we modelled several jets embedded in various ambient medium and torus configurations and subsequently computed the non-thermal emission produced by the jet and thermal absorption from the torus. To better compare the emission simulations with observations we produced synthetic radio maps, taking into account the properties of the observatory. Results: The detailed analysis of our simulations shows that the observed properties such as core shift could be used to distinguish between over-pressured and pressure matched jets. In addition to the properties of the jets, insights into the extent and density of the obscuring torus can be obtained from analyses of the single-dish spectrum and spectral index maps.

Diffuse infrared emission from the galaxy. I. Solar neighborhood

International Nuclear Information System (INIS)

Boulanger, F.; Perault, M.

1988-01-01

A large-scale study of the infrared emission originating in the solar neighborhood based on IRAS data is presented. Away from heating sources and outside molecular clouds, the infrared emission from the ISM is well-correlated with the column density of H I gas. The interstellar radiation field and the dust abundance are roughly uniform on scales of the order of 100 pc. The extinction in the polar caps is discussed, and the origin of the infrared emission from the solar neighborhood is investigated. It is shown that stars younger than a few 100 million yr are responsible for two-thirds of the infrared emission from the solar neighborhood, but that most of this emission comes from interstellar matter not associated with current star formation. The correlation between infrared and radio-continuum fluxes of galaxies breaks down on the scale of a few hundred pc around regions of star formation. 81 references

Latitudinal beaming of Jupiter's low frequency radio emissions

International Nuclear Information System (INIS)

Alexander, J.K.; Desch, M.D.; Kaiser, M.L.; Thieman, J.R.

1979-01-01

By comparing Rae 1 and Imp 6 satelite measurements of Jupiter's radio emissions near 1 MHz with recent Voyager 1 and 2 observations in the same frequency range it is now possible to study the properties of the low frequency radiation pattern over a 10 0 range of latitudes with respect to the Jovian rotation equator. These observations, which cover a wider latitudinal range than is possible from the earth, are consistent with many aspect of earlier ground-based measurements that have been used to infer a sharp beaming pattern for the decameter wavelength emissions. We find marked, systematic changes in the statistical occurrence probability distributions with system III central meridian longitude as the Jovigraphic latitude of the observer changes over this range. Moreover, simultaneous observations by the two Voyager spacecraft, which are separated by up to 3 0 in Jovigraphic latitude, suggest that the instantaneous beam width may be no more than a few degrees at times. The new hectometer wave results can be interpreted in terms of a narrow, curved sheet at a fixed magnetic latitude into which the emission is beamed to escape the planet

Radio emission from the X-ray pulsar Her X-1: a jet launched by a strong magnetic field neutron star?

Science.gov (United States)

van den Eijnden, J.; Degenaar, N.; Russell, T. D.; Miller-Jones, J. C. A.; Wijnands, R.; Miller, J. M.; King, A. L.; Rupen, M. P.

2018-01-01

Her X-1 is an accreting neutron star (NS) in an intermediate-mass X-ray binary. Like low-mass X-ray binaries (LMXBs), it accretes via Roche lobe overflow, but similar to many high-mass X-ray binaries containing a NS; Her X-1 has a strong magnetic field and slow spin. Here, we present the discovery of radio emission from Her X-1 with the Very Large Array. During the radio observation, the central X-ray source was partially obscured by a warped disc. We measure a radio flux density of 38.7 ± 4.8 μJy at 9 GHz but cannot constrain the spectral shape. We discuss possible origins of the radio emission, and conclude that coherent emission, a stellar wind, shocks and a propeller outflow are all unlikely explanations. A jet, as seen in LMXBs, is consistent with the observed radio properties. We consider the implications of the presence of a jet in Her X-1 on jet formation mechanisms and on the launching of jets by NSs with strong magnetic fields.

3D relativistic MHD numerical simulations of X-shaped radio sources

Science.gov (United States)

Rossi, P.; Bodo, G.; Capetti, A.; Massaglia, S.

2017-10-01

Context. A significant fraction of extended radio sources presents a peculiar X-shaped radio morphology: in addition to the classical double lobed structure, radio emission is also observed along a second axis of symmetry in the form of diffuse wings or tails. In a previous investigation we showed the existence of a connection between the radio morphology and the properties of the host galaxies. Motivated by this connection we performed two-dimensional numerical simulations showing that X-shaped radio sources may naturally form as a jet propagates along the major axis a highly elliptical density distribution, because of the fast expansion of the cocoon along the minor axis of the distribution. Aims: We intend to extend our analysis by performing three-dimensional numerical simulations and investigating the role of different parameters in determining the formation of the X-shaped morphology. Methods: The problem is addressed by numerical means, carrying out three-dimensional relativistic magnetohydrodynamic simulations of bidirectional jets propagating in a triaxial density distribution. Results: We show that only jets with power ≲ 1044 erg s-1 can give origin to an X-shaped morphology and that a misalignment of 30° between the jet axis and the major axis of the density distribution is still favourable to the formation of this kind of morphology. In addition we compute synthetic radio emission maps and polarization maps. Conclusions: In our scenario for the formation of X-shaped radio sources only low power FRII can give origin to such kind of morphology. Our synthetic emission maps show that the different observed morphologies of X-shaped sources can be the result of similar structures viewed under different perspectives.

Double-peaked Emission Lines Due to a Radio Outflow in KISSR 1219

Energy Technology Data Exchange (ETDEWEB)

Kharb, P.; Vaddi, S. [National Centre for Radio Astrophysics—Tata Institute of Fundamental Research, Postbag 3, Ganeshkhind, Pune 411007 (India); Subramanian, S. [Kavli Institute for Astronomy and Astrophysics, Peking University, 5 Yiheyuan Road, Haidian District, Beijing 100871 (China); Das, M. [Indian Institute of Astrophysics, II Block, Koramangala, Bangalore 560034 (India); Paragi, Z., E-mail: kharb@ncra.tifr.res.in [Joint Institute for VLBI in Europe, Postbus 2, 7990 AA Dwingeloo (Netherlands)

2017-09-01

We present the results from 1.5 and 5 GHz phase-referenced VLBA and 1.5 GHz Karl G. Jansky Very Large Array (VLA) observations of the Seyfert 2 galaxy KISSR 1219, which exhibits double-peaked emission lines in its optical spectrum. The VLA and VLBA data reveal a one-sided core-jet structure at roughly the same position angles, providing evidence of an active galactic nucleus outflow. The absence of dual parsec-scale radio cores puts the binary black-hole picture in doubt for the case of KISSR 1219. The high brightness temperatures of the parsec-scale core and jet components (>10{sup 6} K) are consistent with this interpretation. Doppler boosting with jet speeds of ≳0.55 c to ≳0.25 c , going from parsec to kiloparsec scales, at a jet inclination ≳50° can explain the jet one-sidedness in this Seyfert 2 galaxy. A blueshifted broad emission line component in [O iii] is also indicative of an outflow in the emission line gas at a velocity of ∼350 km s{sup −1}, while the [O i] doublet lines suggest the presence of shock-heated gas. A detailed line ratio study using the MAPPINGS III code further suggests that a shock+precursor model can explain the line ionization data well. Overall, our data suggest that the radio outflow in KISSR 1219 is pushing the emission line clouds, both ahead of the jet and in a lateral direction, giving rise to the double peak emission line spectra.

A STRING OF RADIO EMISSION ASSOCIATED WITH IRAS 16562-3959: A COLLIMATED JET EMANATING FROM A LUMINOUS MASSIVE YOUNG STELLAR OBJECT

International Nuclear Information System (INIS)

Guzman, Andres E.; Garay, Guido; Brooks, Kate J.

2010-01-01

We report the discovery, made using the Australia Telescope Compact Array, of a remarkable string of radio emission toward IRAS 16562-3959, a luminous infrared source with a bolometric luminosity of 7.0 x 10 4 L sun . The radio emission arises from a compact, bright central component, two inner lobes which are separated by about 7'' and symmetrically offset from the central source, and two outer lobes which are separated by about 45''. The emission from the central object has a spectral index between 1.4 and 8.6 GHz of 0.85 ± 0.15, consistent with free-free emission from a thermal jet. The radio emission from the lobes has spectral indices in the range characteristic of thermal emission. We suggest that the emission from the lobes arises in shocks resulting from the interaction of a collimated wind with the surrounding medium. The radio string is located within a massive dense molecular core, and is associated with extended green emission (Spitzer three-color), Herbig-Haro-type emission (2MASS K s band), and OH maser sites-all phenomena readily observed toward sites of massive star formation. We conclude that the massive core hosts a high-mass star in an early stage of evolution in which it is undergoing the ejection of a powerful collimated stellar wind, showing that jets found in the formation of low-mass stars are also produced in high-mass stars.

THE VLA SURVEY OF CHANDRA DEEP FIELD SOUTH. V. EVOLUTION AND LUMINOSITY FUNCTIONS OF SUB-MILLIJANSKY RADIO SOURCES AND THE ISSUE OF RADIO EMISSION IN RADIO-QUIET ACTIVE GALACTIC NUCLEI

International Nuclear Information System (INIS)

Padovani, P.; Mainieri, V.; Rosati, P.; Miller, N.; Kellermann, K. I.; Tozzi, P.

2011-01-01

We present the evolutionary properties and luminosity functions of the radio sources belonging to the Chandra Deep Field South Very Large Array survey, which reaches a flux density limit at 1.4 GHz of 43 μJy at the field center and redshift ∼5 and which includes the first radio-selected complete sample of radio-quiet active galactic nuclei (AGNs). We use a new, comprehensive classification scheme based on radio, far- and near-IR, optical, and X-ray data to disentangle star-forming galaxies (SFGs) from AGNs and radio-quiet from radio-loud AGNs. We confirm our previous result that SFGs become dominant only below 0.1 mJy. The sub-millijansky radio sky turns out to be a complex mix of SFGs and radio-quiet AGNs evolving at a similar, strong rate; non-evolving low-luminosity radio galaxies; and declining radio powerful (P ∼> 3 x 10 24 W Hz -1 ) AGNs. Our results suggest that radio emission from radio-quiet AGNs is closely related to star formation. The detection of compact, high brightness temperature cores in several nearby radio-quiet AGNs can be explained by the coexistence of two components, one non-evolving and AGN related and one evolving and star formation related. Radio-quiet AGNs are an important class of sub-millijansky sources, accounting for ∼30% of the sample and ∼60% of all AGNs, and outnumbering radio-loud AGNs at ∼< 0.1 mJy. This implies that future, large area sub-millijansky surveys, given the appropriate ancillary multiwavelength data, have the potential of being able to assemble vast samples of radio-quiet AGNs, bypassing the problems of obscuration that plague the optical and soft X-ray bands.

Detection of elusive radio and optical emission from cosmic-ray showers in the 1960s

International Nuclear Information System (INIS)

Fegan, David J.

2012-01-01

During the 1960s, a small but vibrant community of cosmic ray physicists, pioneered novel optical methods of detecting extensive air showers (EAS) in the Earth's atmosphere with the prime objective of searching for point sources of energetic cosmic γ-rays. Throughout that decade, progress was extremely slow. Attempts to use the emission of optical Cherenkov radiation from showers as a basis for TeV gamma-ray astronomy proved difficult and problematical, given the rather primitive light-collecting systems in use at the time, coupled with a practical inability to reject the overwhelming background arising from hadronic showers. Simultaneously, a number of groups experimented with passive detection of radio emission from EAS as a possible cheap, simple, stand-alone method to detect and characterise showers of energy greater than 10 16 eV. By the end of the decade, it was shown that the radio emission was quite highly beamed and hence the effective collection area for detection of high energy showers was quite limited, diminishing the effectiveness of the radio signature as a stand-alone shower detection channel. By the early 1970s much of the early optimism for both the optical and radio techniques was beginning to dissipate, greatly reducing research activity. However, following a long hiatus both avenues were in time revived, the optical in the early 1980s and the radio in the early 2000s. With the advent of digital logic hardware, powerful low-cost computing, the ability to perform Monte Carlo simulations and above all, greatly improved funding, rapid progress became possible. In time this work proved to be fundamental to both High Energy γ-ray Astronomy and Neutrino Astrophysics. Here, that first decade of experimental investigation in both fields is reviewed.

Detection of elusive radio and optical emission from cosmic-ray showers in the 1960s

Energy Technology Data Exchange (ETDEWEB)

Fegan, David J., E-mail: david.fegan@ucd.ie [School of Physics, University College Dublin, Dublin 4 (Ireland)

2012-01-11

During the 1960s, a small but vibrant community of cosmic ray physicists, pioneered novel optical methods of detecting extensive air showers (EAS) in the Earth's atmosphere with the prime objective of searching for point sources of energetic cosmic {gamma}-rays. Throughout that decade, progress was extremely slow. Attempts to use the emission of optical Cherenkov radiation from showers as a basis for TeV gamma-ray astronomy proved difficult and problematical, given the rather primitive light-collecting systems in use at the time, coupled with a practical inability to reject the overwhelming background arising from hadronic showers. Simultaneously, a number of groups experimented with passive detection of radio emission from EAS as a possible cheap, simple, stand-alone method to detect and characterise showers of energy greater than 10{sup 16} eV. By the end of the decade, it was shown that the radio emission was quite highly beamed and hence the effective collection area for detection of high energy showers was quite limited, diminishing the effectiveness of the radio signature as a stand-alone shower detection channel. By the early 1970s much of the early optimism for both the optical and radio techniques was beginning to dissipate, greatly reducing research activity. However, following a long hiatus both avenues were in time revived, the optical in the early 1980s and the radio in the early 2000s. With the advent of digital logic hardware, powerful low-cost computing, the ability to perform Monte Carlo simulations and above all, greatly improved funding, rapid progress became possible. In time this work proved to be fundamental to both High Energy {gamma}-ray Astronomy and Neutrino Astrophysics. Here, that first decade of experimental investigation in both fields is reviewed.

IRAS observations of radio-quiet and radio-loud quasars

Science.gov (United States)

Neugebauer, G.; Soifer, B. T.; Miley, G.; Habing, H. J.; Young, E.; Low, F. J.; Beichman, C. A.; Clegg, P. E.; Harris, S.; Rowan-Robinson, M.

1984-01-01

Observations from 12 to 100 microns are presented of two radio-quiet and three radio-loud quasars. Over this wavelength range, all five have grossly similar continuum energy distributions. The continua of the radio-loud quasars are consistent with synchrotron radiation. There is an indication, however, of excess 100 micron emission in the two radio-quiet quasars.

On the nature of emission of the star-gas-dust complex of the W1 radio source

International Nuclear Information System (INIS)

Udal'tsov, V.A.; Kovalenko, A.V.

1982-01-01

The brightness distribution of the radio source W 1 at 102 MHz has been investigated with the 187x384 m radio telescope in Pushchino. It is shown that W 1 is genetically connected with the stellar association Ceph IV as well as with the extended emission nebula GS 285 which consists of numerous nebulae, including two bright ones, Sharpless (S) 171 and NGC 7822. The radio emission of the nebula S 171 is shown to be thermal, and there is no Supernova remnant in it, in contrast with the other authors' suggestion. By two independent methods, the distance to S 171 has been evaluated to be 840 pc. The emission of NGC 7822 is mainly thermal. The extended nebula GS 285 is a thermal source, not a remnant of a Supernova that had exploded in a dense gas - dust medium, as was believed by other authors. Attention is drawn to the wrong identification by many authors of the radio source in the S 171 region with the nebula NGC 7822. It is shown that when measuring the difference of spectral indices of two sources, the calibration error may be eliminated if their calibration at given frequency is made by means of the same source [ru

Limits on radio emission from meteors using the MWA

Science.gov (United States)

Zhang, Xiang; Hancock, Paul; Devillepoix, Hadrien A. R.; Wayth, Randall B.; Beardsley, A.; Crosse, B.; Emrich, D.; Franzen, T. M. O.; Gaensler, B. M.; Horsley, L.; Johnston-Hollitt, M.; Kaplan, D. L.; Kenney, D.; Morales, M. F.; Pallot, D.; Steele, K.; Tingay, S. J.; Trott, C. M.; Walker, M.; Williams, A.; Wu, C.; Ji, Jianghui; Ma, Yuehua

2018-04-01

Recently, low frequency, broadband radio emission has been observed accompanying bright meteors by the Long Wavelength Array (LWA). The broadband spectra between 20 and 60 MHz were captured for several events, while the spectral index (dependence of flux density on frequency, with Sν∝να) was estimated to be -4 ± 1 during the peak of meteor afterglows. Here we present a survey of meteor emission and other transient events using the Murchison Widefield Array (MWA) at 72-103 MHz. In our 322-hour survey, down to a 5σ detection threshold of 3.5 Jy/beam, no transient candidates were identified as intrinsic emission from meteors. We derived an upper limit of -3.7 (95% confidence limit) on the spectral index in our frequency range. We also report detections of other transient events, like reflected FM broadcast signals from small satellites, conclusively demonstrating the ability of the MWA to detect and track space debris on scales as small as 0.1 m in low Earth orbits.

Solar Plasma Radio Emission in the Presence of Imbalanced Turbulence of Kinetic-Scale Alfvén Waves

Science.gov (United States)

Lyubchyk, O.; Kontar, E. P.; Voitenko, Y. M.; Bian, N. H.; Melrose, D. B.

2017-09-01

We study the influence of kinetic-scale Alfvénic turbulence on the generation of plasma radio emission in the solar coronal regions where the ratio β of plasma to magnetic pressure is lower than the electron-to-ion mass ratio me/mi. The present study is motivated by the phenomenon of solar type I radio storms that are associated with the strong magnetic field of active regions. The measured brightness temperature of the type I storms can be up to 10^{10} K for continuum emission, and can exceed 10^{11} K for type I bursts. At present, there is no generally accepted theory explaining such high brightness temperatures and some other properties of the type I storms. We propose a model with an imbalanced turbulence of kinetic-scale Alfvén waves that produce an asymmetric quasi-linear plateau on the upper half of the electron velocity distribution. The Landau damping of resonant Langmuir waves is suppressed and their amplitudes grow spontaneously above the thermal level. The estimated saturation level of Langmuir waves is high enough to generate observed type I radio emission at the fundamental plasma frequency. Harmonic emission does not appear in our model because the backward-propagating Langmuir waves undergo strong Landau damping. Our model predicts 100% polarization in the sense of the ordinary (o-) mode of type I emission.

X rays from radio binaries

International Nuclear Information System (INIS)

Apparao, K.M.V.

1977-01-01

Reference is made to the radio binary systems CC Cas, AR Lac, β Per (Algol), β Lyr, b Per and Cyg X-1. It is stated that a thermal interpretation of the radiation from Algol requires a much larger x-ray flux than the observed value of 3.8 x 10 -11 erg/cm 2 /sec/keV in the 2 to 6 keV energy range. Observations of some non-thermal flares, together with the small size of the radio source in Algol, indicate that the radio emission is non-thermal in nature. The radio emission is interpreted as synchrotron radiation and it is suggested that the observed x-ray emission is due to inverse Compton scattering of the light of the primary star by the radio electrons. The x-ray emission from other radio binaries is also calculated using this model. The energy for the radio electrons can arise from annihilation of magnetic lines connecting the binary stars, twisted by the rotation of the stars. (U.K.)

On the secular decrease of radio emission flux densities of the supernova remnants of Cassiopeia A and Taurus A at frequency 927 MHz

International Nuclear Information System (INIS)

Vinyajkin, E.N.; Razin, V.A.

1979-01-01

Relative measurements of the radio emission flux densities of the supernova remnants of Cassiopeia A and Taurus A were made at the frequency 927 MHz to investigate the secular decrease of their intensity. Experiments were fulfilled in October-December 1977 at the 10-meter radio telescope of the radioastronomical station Staraya Pustyn' (NIRFI). The radio galaxied of Cygnus A, Virgo A and Orion Nebula were taken as the comparison sources. The comparison of the data obtained with the results of absolute measurements carried out in October 1962 permits to state that during 15 years the radio emission flux density of Cassiopeia A decreased by (14.2+-0.6)% (the average annual decrease amounts to (0.95+-O.04)%) and the radio emission flux density of Taurus A decreased by (2.7+-0.1)% (the annual decrease is (0.18+-0.01)%)

THE NON-THERMAL, TIME-VARIABLE RADIO EMISSION FROM Cyg OB2 no. 5: A WIND-COLLISION REGION

International Nuclear Information System (INIS)

Ortiz-Leon, Gisela N.; Loinard, Laurent; RodrIguez, Luis F.; Dzib, Sergio A.; Mioduszewski, Amy J.

2011-01-01

The radio emission from the well-studied massive stellar system Cyg OB2 no. 5 is known to fluctuate with a period of 6.7 years between a low-flux state, when the emission is entirely of free-free origin, and a high-flux state, when an additional non-thermal component (of hitherto unknown nature) appears. In this paper, we demonstrate that the radio flux of that non-thermal component is steady on timescales of hours and that its morphology is arc-like. This shows that the non-thermal emission results from the collision between the strong wind driven by the known contact binary in the system and that of an unseen companion on a somewhat eccentric orbit with a 6.7 year period and a 5-10 mas semimajor axis. Together with the previously reported wind-collision region located about 0.''8 to the northeast of the contact binary, so far Cyg OB2 no. 5 appears to be the only multiple system known to harbor two radio-imaged wind-collision regions.

Solar radio observations and interpretations

International Nuclear Information System (INIS)

Rosenberg, H.

1976-01-01

The recent solar radio observations related to flares are reviewed for the frequency range of a few kilohertz to several gigahertz. The analysis of the radio data leads to boundary conditions on the acceleration processes which are responsible for the fast particles which cause radio emission. The role and cause of plasma turbulence at the plasma-frequency and at much lower frequencies is discussed in relation to the acceleration processes and the radio emission mechanisms for the various radio bursts. (author)

Bright radio emission from an ultraluminous stellar-mass microquasar in M 31

NARCIS (Netherlands)

Middleton, M.J.; Miller Jones, J.C.A.; Markoff, S.; Fender, R.; Henze, M.; Hurley-Walker, N.; Scaife, A.M.M.; Roberts, T.P.; Walton, D.; Carpenter, J.; Macquart, J.-P.; Bower, G.C.; Gurwell, G.; Pietsch, W.; Haberl, F.; Harris, J.; Daniel, M.; Miah, J.; Done, C.; Morgan, J.S.; Dickinson, H.; Charles, P.; Burwitz, V.; Della Valle, M.; Freyberg, M.; Greiner, J.; Hernanz, M.; Hartmann, D.H.; Hatzidimitriou, D.; Riffeser, A.; Sala, G.; Seitz, S.; Reig, P.; Rau, A.; Orio, M.; Titterington, D.; Grainge, K.

2013-01-01

A subset of ultraluminous X-ray sources (those with luminosities of less than 1040 erg s−1; ref. 1) are thought to be powered by the accretion of gas onto black holes with masses of ~5-20 , probably by means of an accretion disk2, 3. The X-ray and radio emission are coupled in such Galactic sources;

POLARIZED EXTENDED Ly{alpha} EMISSION FROM A z = 2.3 RADIO GALAXY

Energy Technology Data Exchange (ETDEWEB)

Humphrey, A. [Centro de Astrofisica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Vernet, J.; Fosbury, R. A. E. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Villar-Martin, M. [Centro de Astrobiologia (INTA-CSIC), Carretera de Ajalvir, km 4, E-28850 Torrejon de Ardoz, Madrid (Spain); Di Serego Alighieri, S. [INAF-Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, I-50125 Firenze (Italy); Cimatti, A., E-mail: andrew.humphrey@astro.up.pt [Dipartimento di Astronomia, Universita di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)

2013-05-01

We present spatially resolved spectropolarimetric measurements of the 100 kpc scale gaseous environment of the z = 2.34 radio galaxy TXS 0211-122. The polarization level of the narrow Ly{alpha} emission is low centrally (P < 5%), but rises to P = 16.4% {+-} 4.6% in the eastern part of the nebula, indicating that the nebula is at least partly powered by the scattering of Ly{alpha} photons by H I. Not only is this the first detection of polarized Ly{alpha} around a radio-loud active galaxy, it is also the second detection to date for any kind of Ly{alpha} nebula. We also detect a pair of diametrically opposed UV continuum sources along the slit, at the outer edges of the Ly{alpha} nebula, which we suggest may be the limb of a dusty shell, related to the large-scale H I absorbers often associated with high-z radio galaxies.

Radio Emission from Pulsar Wind Nebulae without Surrounding Supernova Ejecta: Application to FRB 121102

Energy Technology Data Exchange (ETDEWEB)

Dai, Z. G.; Wang, J. S. [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Yu, Y. W., E-mail: dzg@nju.edu.cn [Institute of Astrophysics, Central China Normal University, Wuhan 430079 (China)

2017-03-20

In this paper, we propose a new scenario in which a rapidly rotating strongly magnetized pulsar without any surrounding supernova ejecta repeatedly produces fast radio bursts (FRBs) via a range of possible mechanisms; simultaneously, an ultra-relativistic electron/positron pair wind from the pulsar sweeps up its ambient dense interstellar medium, giving rise to a non-relativistic pulsar wind nebula (PWN). We show that the synchrotron radio emission from such a PWN is bright enough to account for the recently discovered persistent radio source associated with the repeating FRB 121102 within reasonable ranges of the model parameters. Our PWN scenario is consistent with the non-evolution of the dispersion measure inferred from all of the repeating bursts observed in four years.

Radio Emission from Pulsar Wind Nebulae without Surrounding Supernova Ejecta: Application to FRB 121102

International Nuclear Information System (INIS)

Dai, Z. G.; Wang, J. S.; Yu, Y. W.

2017-01-01

In this paper, we propose a new scenario in which a rapidly rotating strongly magnetized pulsar without any surrounding supernova ejecta repeatedly produces fast radio bursts (FRBs) via a range of possible mechanisms; simultaneously, an ultra-relativistic electron/positron pair wind from the pulsar sweeps up its ambient dense interstellar medium, giving rise to a non-relativistic pulsar wind nebula (PWN). We show that the synchrotron radio emission from such a PWN is bright enough to account for the recently discovered persistent radio source associated with the repeating FRB 121102 within reasonable ranges of the model parameters. Our PWN scenario is consistent with the non-evolution of the dispersion measure inferred from all of the repeating bursts observed in four years.

Radio Emission from Supernovae

International Nuclear Information System (INIS)

Weiler, Kurt W.; Panagia, Nino; Sramek, Richard A.; Van Dyk, Schuyler D.; Williams, Christopher L.; Stockdale, Christopher J.; Kelley, Matthew T.

2009-01-01

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.

Outer heliospheric radio emissions. II - Foreshock source models

Science.gov (United States)

Cairns, Iver H.; Kurth, William S.; Gurnett, Donald A.

1992-01-01

Observations of LF radio emissions in the range 2-3 kHz by the Voyager spacecraft during the intervals 1983-1987 and 1989 to the present while at heliocentric distances greater than 11 AU are reported. New analyses of the wave data are presented, and the characteristics of the radiation are reviewed and discussed. Two classes of events are distinguished: transient events with varying starting frequencies that drift upward in frequency and a relatively continuous component that remains near 2 kHz. Evidence for multiple transient sources and for extension of the 2-kHz component above the 2.4-kHz interference signal is presented. The transient emissions are interpreted in terms of radiation generated at multiples of the plasma frequency when solar wind density enhancements enter one or more regions of a foreshock sunward of the inner heliospheric shock. Solar wind density enhancements by factors of 4-10 are observed. Propagation effects, the number of radiation sources, and the time variability, frequency drift, and varying starting frequencies of the transient events are discussed in terms of foreshock sources.

Aperture synthesis observations of solar and stellar radio emission

International Nuclear Information System (INIS)

Bastian, T.S.

1987-01-01

The work presented in this thesis relied upon the radio astronomical instrument, The Very Large Array. The thesis is divided into three major sections. In the first the author applied maximum entropy-type image reconstruction techniques, using both single dish and iterferometer data, to generate full disk images of the Sun at a wavelength λ ∼ 21 cm. Using a set of six such images obtained during the Sun's decline from sunspot maximum to minimum, he has noted a number of previously unreported phenomena. Among these: (1) a systematic decrease in quiet Sun's brightness temperature as it declined to minimum; (2) a systematic decrease in the Sun's radius at 21 cm; (3) evidence for the evolution of polar coronal holes during the course of the solar cycle. The observed variation, though not noted previously at radio wavelengths, is entirely consistent with white light K coronagraph data. The results reported here explain the conflicting nature of a number of past observations. In the second section of the thesis, he presents the results of a long term survey of magnetic cataclysmic variables (CVs). Cataclysmic variables are close binary systems which contain a white dwarf accreting mass from a late-type secondary, typically a dwarf of spectral type, G, K, or M. The survey resulted in the detection of two out of the eighteen systems observed. In the third section of the thesis, he presents new results on flare stars in the solar neighborhood and in the Pleiades. He has successfully employed the technique of dynamic spectroscopy to constrain the mechanisms(s) for radio flaring on other stars. The second part of section three is devoted to a search for radio emission from flare stars in the Pleiades which was motivated by the evolutionary questions raised by flare stars and the Pleiades lower main sequence

THE ORIGIN OF THE INFRARED EMISSION IN RADIO GALAXIES. II. ANALYSIS OF MID- TO FAR-INFRARED SPITZER OBSERVATIONS OF THE 2JY SAMPLE

International Nuclear Information System (INIS)

Dicken, D.; Tadhunter, C.; Axon, D.; Morganti, R.; Inskip, K. J.; Holt, J.; Groves, B.; Delgado, R. Gonzalez

2009-01-01

We present an analysis of deep mid- to far-infrared (MFIR) Spitzer photometric observations of the southern 2Jy sample of powerful radio sources (0.05 < z < 0.7), conducting a statistical investigation of the links between radio jet, active galactic nucleus (AGN), starburst activity and MFIR properties. This is part of an ongoing extensive study of powerful radio galaxies that benefits from both complete optical emission line information and a uniquely high detection rate in the far-infrared (far-IR). We find tight correlations between the MFIR and [O III]λ5007 emission luminosities, which are significantly better than those between MFIR and extended radio luminosities, or between radio and [O III] luminosities. Since [O III] is a known indicator of intrinsic AGN power, these correlations confirm AGN illumination of the circumnuclear dust as the primary heating mechanism for the dust producing thermal MFIR emission at both 24 and 70 μm. We demonstrate that AGN heating is energetically feasible, and identify the narrow-line region clouds as the most likely location of the cool, far-IR emitting dust. Starbursts make a major contribution to the heating of the cool dust in only 15%-28% of our targets. We also investigate the orientation dependence of the continuum properties, finding that the broad- and narrow-line objects in our sample with strong emission lines have similar distributions of MFIR luminosities and colors. Therefore our results are entirely consistent with the orientation-based unified schemes for powerful radio galaxies. However, the weak line radio galaxies form a separate class of objects with intrinsically low-luminosity AGNs in which both the optical emission lines and the MFIR continuum are weak.

Saturn radio emission and the solar wind - Voyager-2 studies

International Nuclear Information System (INIS)

Desch, M.D.; Rucker, H.O.; Observatorium Lustbuhel, Graz, Austria)

1985-01-01

Voyager 2 data from the Plasma Science experiment, the Magnetometer experiment and the Planetary Radio Astronomy experiment were used to analyze the relationship between parameters of the solar wind/interplanetary medium and the nonthermal Saturn radiation. Solar wind and interplanetary magnetic field properties were combined to form quantities known to be important in controlling terrestrial magnetospheric processes. The Voyager 2 data set used in this investigation consists of 237 days of Saturn preencounter measurements. However, due to the immersion of Saturn and the Voyager 2 spacecraft into the extended Jupiter magnetic tail, substantial periods of the time series were lacking solar wind data. To cope with this problem a superposed epoch method (CHREE analysis) was used. The results indicate the superiority of the quantities containing the solar wind density in stimulating the radio emission of Saturn - a result found earlier using Voyager 1 data - and the minor importance of quantities incorporating the interplanetary magnetic field. 10 references

FAR-UV EMISSION PROPERTIES OF FR1 RADIO GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Danforth, Charles W.; Stocke, John T.; France, Kevin; Begelman, Mitchell C. [Department of Astrophysical and Planetary Sciences, University of Colorado, 391-UCB, Boulder, CO 80309 (United States); Perlman, Eric, E-mail: danforth@colorado.edu [Department of Physics and Space Sciences, Florida Institute of Technology, 150 W. University Boulevard, Melbourne, FL 32901 (United States)

2016-11-20

The power mechanism and accretion geometry for low-power FR 1 radio galaxies are poorly understood in comparison to those for Seyfert galaxies and QSOs. In this paper, we use the diagnostic power of the Ly α recombination line observed using the Cosmic Origins Spectrograph (COS) aboard the Hubble Space Telescope ( HST ) to investigate the accretion flows in three well-known, nearby FR 1s: M87, NGC 4696, and Hydra A. The Ly α emission line’s luminosity, velocity structure, and the limited knowledge of its spatial extent provided by COS are used to assess conditions within a few parsecs of the supermassive black hole in these radio-mode active galactic nuclei. We observe strong Ly α emission in all three objects with total luminosity similar to that seen in BL Lacertae objects. M87 shows a complicated emission-line profile in Ly α , which varies spatially across the COS aperture and possibly temporally over several epochs of observation. In both NGC 4696 and M87, the Ly α luminosities ∼10{sup 40} erg s{sup -1} are closely consistent with the observed strength of the ionizing continuum in Case B recombination theory and with the assumption of a near-unity covering factor. It is possible that the Ly α -emitting clouds are ionized largely by beamed radiation associated with the jets. Long-slit UV spectroscopy can be used to test this hypothesis. Hydra A and the several BL Lac objects studied in this and previous papers have Ly α luminosities larger than M87 but their extrapolated, nonthermal continua are so luminous that they overpredict the observed strength of Ly α , a clear indicator of relativistic beaming in our direction. Given their substantial space density (∼4 × 10{sup -3} Mpc{sup -3}), the unbeamed Lyman continuum radiation of FR 1s may make a substantial minority contribution (∼10%) to the local UV background if all FR 1s are similar to M87 in ionizing flux level.

The mystery of the "Kite" radio source in Abell 2626: Insights from new Chandra observations

Science.gov (United States)

Ignesti, A.; Gitti, M.; Brunetti, G.; O'Sullivan, E.; Sarazin, C.; Wong, K.

2018-03-01

Context. We present the results of a new Chandra study of the galaxy cluster Abell 2626. The radio emission of the cluster shows a complex system of four symmetric arcs without known correlations with the thermal X-ray emission. The mirror symmetry of the radio arcs toward the center and the presence of two optical cores in the central galaxy suggested that they may be created by pairs of precessing radio jets powered by dual active galactic nuclei (AGNs) inside the core dominant galaxy. However, previous observations failed to observe the second jetted AGN and the spectral trend due to radiative age along the radio arcs, thus challenging this interpretation. Aim. The new Chandra observation had several scientific objectives, including the search for the second AGN that would support the jet precession model. We focus here on the detailed study of the local properties of the thermal and non-thermal emission in the proximity of the radio arcs, in order to obtain further insights into their origin. Methods: We performed a standard data reduction of the Chandra dataset deriving the radial profiles of temperature, density, pressure and cooling time of the intra-cluster medium. We further analyzed the two-dimensional (2D) distribution of the gas temperature, discovering that the south-western junction of the radio arcs surrounds the cool core of the cluster. Results: We studied the X-ray surface brightness and spectral profiles across the junction, finding a cold front spatially coincident with the radio arcs. This may suggest a connection between the sloshing of the thermal gas and the nature of the radio filaments, raising new scenarios for their origin. A tantalizing possibility is that the radio arcs trace the projection of a complex surface connecting the sites where electrons are most efficiently reaccelerated by the turbulence that is generated by the gas sloshing. In this case, diffuse emission embedded by the arcs and with extremely steep spectrum should be

Jet emission in young radio sources: A Fermi large area telescope gamma-ray view

Energy Technology Data Exchange (ETDEWEB)

Migliori, G.; Siemiginowska, A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Kelly, B. C. [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93107 (United States); Stawarz, Ł. [Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Celotti, A. [Scuola Internazionale Superiore di Studi Avanzati (SISSA), via Bonomea, 265-34136 Trieste (Italy); Begelman, M. C., E-mail: migliori@cfa.harvard.edu [JILA, University of Colorado and National Institute of Standards and Technology, 440 UCB, Boulder, CO 80309-0440 (United States)

2014-01-10

We investigate the contribution of the beamed jet component to the high-energy emission in young and compact extragalactic radio sources, focusing for the first time on the γ-ray band. We derive predictions on the γ-ray luminosities associated with the relativistic jet assuming a leptonic radiative model. The high-energy emission is produced via Compton scattering by the relativistic electrons in a spherical region at the considered scales (≲10 kpc). Simulations show a wide range of γ-ray luminosities, with intensities up to ∼10{sup 46}-10{sup 48} erg s{sup –1} depending on the assumed jet parameters. We find a highly linear relation between the simulated X-ray and γ-ray luminosities that can be used to select candidates for γ-ray detection. We compare the simulated luminosity distributions in the radio, X-ray, and γ-ray regimes with observations for the largest sample of X-ray-detected young radio quasars. Our analysis of ∼4-yr Fermi Large Area Telescope (LAT) data does not yield any statistically significant detections. However, the majority of the model-predicted γ-ray fluxes for the sample are near or below the current Fermi-LAT flux threshold and compatible with the derived upper limits. Our study gives constraints on the minimum jet power (L {sub jet,} {sub kin}/L {sub disk} > 0.01) of a potential jet contribution to the X-ray emission in the most compact sources (≲ 1 kpc) and on the particle-to-magnetic field energy density ratio that are in broad agreement with equipartition assumptions.

Resonators for magnetohydrodynamic waves in the solar corona: The effect of modulation of radio emission

International Nuclear Information System (INIS)

Zaitsev, V.V.; Stepanov, A.V.

1982-01-01

It is shown that the existence of a minimum of the Alfven speed in the corona at a height of approx.1R/sub sun/ follows from the characteristics of type II radio bursts. The region of a reduced Alfven speed is a resonator for a fast magnetosonic (FMS) waves. The eigenmodes of the resonator are determined. The period of the fundamental mode has the order of several minutes. In the resonator FMS waves can be excited at the Cherenkov resonance by streams of energetic ions. Modulations of metal solar radio emission with a period of several minutes is explained by the effect of the propagation of radio waves through an oscillating magnetohydrodynamic (MHD) resonator

Radio emission from supernovae. I. One to twelve year old supernovae

International Nuclear Information System (INIS)

Weiler, K.W.; Panagia, N.; Sramek, R.A.; Van Der Hulst, J.M.; Roberts, M.S.

1989-01-01

All recorded optical supernovae brighter than 14.0 mag from SN 1970A to SN 1981A were observed in May 1982 using VLA at 6 cm. Apart from the known radio supernovae (SN 1970G, SN 1979C, and SN 1980K), radio emissions were not detected from any of the objects to a limit of about 0.5 mJy. Limits on mass-loss rates from the presupernova systems are established. It is found that Type Ia Sns originate in systems which contain very little circumstellar material at the time of explosion. These systems are very different from those which originate Type Ib Sns. With some exceptions, Type II SNs originate with the high presupernova mass-loss rates expected from red supergiant progenitors with original main-sequence masses greater than about 8 solar masses. 16 references

Diffuse and fugitive emission dose assessment on the Hanford Site

International Nuclear Information System (INIS)

Davis, W.E.; Schmidt, J.W.; Gleckler, B.P.; Rhoads, K.

1995-01-01

On February 3, 1993, the US Department of Energy, Richland Operations Office (RL), received a Compliance Order and Information Request from the Director of the Air and Toxics Division of the US Environmental Protection Agency (EPA), Region 10. The Compliance Order requires RL to (1) evaluate all radionuclide emission points at the Hanford Site to determine which are subject to continuous emission measurement requirements in 40 Code of Federal Regulations (CFR) 61, Subpart H, and (2) continuously measure radionuclide emissions in accordance with 40 CFR 61.93. The Information Request requires RL to provide a written Compliance Plan to meet the requirements of the Compliance Order. The RL Compliance Plan included as one of its milestones the requirement to develop a Federal Facility Compliance Agreement (FFCA). An FFCA was negotiated between RL and the EPA, Region 10, and was entered into on February 7, 1994. One of the milestones was to provide EPA, Region 10, with a copy of the Federal Clean Air Act Title V operating air permit application and Air Emission Inventory (AEI) concurrent with its submission to the Washington State Department of Ecology. The AEI will include an assessment of the diffuse and fugitive emissions from the Hanford Site. This assessment does not identify any diffuse or fugitive emission source that would cause an effective dose equivalent greater than 0.1 mrem/yr

RADIO MONITORING OF THE PERIODICALLY VARIABLE IR SOURCE LRLL 54361: NO DIRECT CORRELATION BETWEEN THE RADIO AND IR EMISSIONS

Energy Technology Data Exchange (ETDEWEB)

Forbrich, Jan, E-mail: jan.forbrich@univie.ac.at [University of Vienna, Department of Astrophysics, Türkenschanzstraße 17, A-1180 Vienna (Austria); Rodríguez, Luis F.; Palau, Aina; Zapata, Luis A. [Instituto de Radioastronomía y Astrofísica, UNAM, Apdo. Postal 3-72 (Xangari), 58089 Morelia, Michoacán (Mexico); Muzerolle, James [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Gutermuth, Robert A. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States)

2015-11-20

LRLL 54361 is an infrared source located in the star-forming region IC 348 SW. Remarkably, its infrared luminosity increases by a factor of 10 over roughly one week every 25.34 days. To understand the origin of these remarkable periodic variations, we obtained sensitive 3.3 cm JVLA radio continuum observations of LRLL 54361 and its surroundings in six different epochs: three of them during the IR-on state and three during the IR-off state. The radio source associated with LRLL 54361 remained steady and did not show a correlation with the IR variations. We suggest that the IR is tracing the results of fast (with a timescale of days) pulsed accretion from an unseen binary companion, while the radio traces an ionized outflow with an extent of ∼100 AU that smooths out the variability over a period of the order of a year. The average flux density measured in these 2014 observations, 27 ± 5 μJy, is about a factor of two less than that measured about 1.5 years before, 53 ± 11 μJy, suggesting that variability in the radio is present, but over larger timescales than in the IR. We discuss other sources in the field, in particular two infrared/X-ray stars that show rapidly varying gyrosynchrotron emission.

Radio Thermal Emission from Pluto and Charon during the New Horizons Encounter

Science.gov (United States)

Bird, Michael; Linscott, Ivan; Hinson, David; Tyler, G. L.; Strobel, Darrell F.; New Horizons Science Team

2017-10-01

As part of the New Horizons Radio-Science Experiment REX, radio thermal emission from Pluto and Charon (wavelength: 4.2 cm) was observed during the encounter on 14 July 2015. The primary REX measurement, a determination of the atmospheric height profile from the surface up to about 100 km, was conducted during an uplink radio occultation at both ingress and egress (Hinson et al., Icarus 290, 96-111, 2017). During the interval between ingress and egress, when the Earth and the REX uplink signals were occulted by the Pluto disk, the spacecraft antenna continued to point toward Earth and thus scanned diametrically across the Pluto nightside. The average diameter of the HGA 3 dB beam was ≈1100 km at the surface during this opportunity, thereby providing crudely resolved measurements of the radio brightness temperature across Pluto. The best resolution for the REX radiometry observations occurred shortly after closest approach, when the HGA was scanned twice across Pluto. These observations will be reported elsewhere (Linscott et al., Icarus, submitted, 2017). In addition to the resolved observations, full disk brightness temperature measurements of both bodies were performed during the approach (dayside) and departure (nightside) phases of the encounter. We present the results of these observations and provide a preliminary interpretation of the measured brightness temperatures.

Search for EAS radio-emission at the Tien-Shan shower installation at a height of 3340 m above sea level

Science.gov (United States)

Beisenova, A.; Boos, E.; Haungs, A.; Sadykov, T.; Salihov, N.; Shepetov, A.; Tautayev, Y.; Vildanova, L.; Zhukov, V.

2017-06-01

The complex EAS installation of the Tien Shan mountain cosmic ray station which is situated at a height of 3340 m above sea level includes the scintillation and Cherenkov detectors of charged shower particles, an ionization calorimeter and a set of neutron detectors for registering the hadronic component of the shower, and a number of underground detectors of the penetrative EAS component. Now it is intended to expand this installation with a promising method for detecting the radio-emission generated by the particles of the developing shower. The facility for radio-emission detection consists of a three crossed dipole antennae, one being set vertically, and another two - mutually perpendicularly in a horizontal plane, all of them being connected to a three-channel radio-frequency amplifier of German production. By the passage of an extensive air shower, which is defined by a scintillation shower detector system, the output signal of antenna amplifier is digitized by a fast multichannel DT5720 ADC of Italian production, and kept within computer memory. The further analysis of the detected signal anticipates its operation according to a special algorithm and a search for the pulse of radio-emission from the shower. A functional test of the radio-installation is made with artificial signals which imitate those of the shower, and with the use of a N1996A type wave analyzer of Agilent Technologies production. We present preliminary results on the registration of extensive air shower emission at the Tien Shan installation which were collected during test measurements held in Summer 2016.

Advanced Diagnostics for the Study of Linearly Polarized Emission. II. Application to Diffuse Interstellar Radio Synchrotron Emission

Science.gov (United States)

Herron, C. A.; Burkhart, Blakesley; Gaensler, B. M.; Lewis, G. F.; McClure-Griffiths, N. M.; Bernardi, G.; Carretti, E.; Haverkorn, M.; Kesteven, M.; Poppi, S.; Staveley-Smith, L.

2018-03-01

Diagnostics of polarized emission provide us with valuable information on the Galactic magnetic field and the state of turbulence in the interstellar medium, which cannot be obtained from synchrotron intensity alone. In Paper I, we derived polarization diagnostics that are rotationally and translationally invariant in the Q–U plane, similar to the polarization gradient. In this paper, we apply these diagnostics to simulations of ideal magnetohydrodynamic turbulence that have a range of sonic and Alfvénic Mach numbers. We generate synthetic images of Stokes Q and U for these simulations for the cases where the turbulence is illuminated from behind by uniform polarized emission and where the polarized emission originates from within the turbulent volume. From these simulated images, we calculate the polarization diagnostics derived in Paper I for different lines of sight relative to the mean magnetic field and for a range of frequencies. For all of our simulations, we find that the polarization gradient is very similar to the generalized polarization gradient and that both trace spatial variations in the magnetoionic medium for the case where emission originates within the turbulent volume, provided that the medium is not supersonic. We propose a method for distinguishing the cases of emission coming from behind or within a turbulent, Faraday rotating medium and a method to partly map the rotation measure of the observed region. We also speculate on statistics of these diagnostics that may allow us to constrain the physical properties of an observed turbulent region.

Radio continuum processes in clusters of galaxies; Proceedings of the Workshop, Green Bank, WV, Aug. 4-8, 1986

International Nuclear Information System (INIS)

O'dea, C.P.; Uson, J.M.

1986-01-01

Recent observational and theoretical investigations of clusters of galaxies are examined in reviews and reports. Topics addressed include radio surveys of clusters, accretion flows, wide-angle-tail radio sources, the interaction of radio sources with the intracluster medium, diffuse emission in clusters, cluster dynamics, and the environment of powerful radio sources. Particular attention is given to a local perspective on galaxies in rich clusters, X-ray observations of clusters, VLA observations of distant clusters, the halo of Vir A at 327 MHz, Exosat observations of the Vir Cluster, accretion flows in elliptical galaxies, jet disruption in wide-angle-tail radio galaxies, beam trajectories in the intracluster medium, the Suniaev-Zel'dovich effect, dark matter in clusters, and the H I environment of high-redshift quasars

Assessment of patients with diffuse pigmented Villonodular Synovitis of Knee before and after radio-synovectomy

International Nuclear Information System (INIS)

Koca, G.; Ozsoy, H.; Atilgan, H.I.; Baskin, A.; Koray, D.; Fakioglu, O.; Korkmaz, M.

2015-01-01

Full text of publication follows. Aim: the aim of this study was to evaluate subjective and objective findings of patients with diffuse pigmented villonodular synovitis (DPVNS) of knee before and after treatment with Yttrium-90 (Y-90) radio-synovectomy. Materials and methods: between years 2005 and 2013, 23 patients, 15 female and 8 male, who had adjuvant radio-synovectomy after arthroscopic surgery were included to our study. 5 mCi of Y-90 radiocolloid was administered under local anesthesia at least 6 weeks after arthroscopic surgery. The patients were reevaluated 6 months after radio-synovectomy. All the patients were assigned a Lysholm knee score prior to surgery, prior to radio-synovectomy and 6 months after radio-synovectomy. Lysholm score was calculated according to patients' pain, swelling, instability, locking, limping, support, climbing the stairs, squatting and the highest evaluation score was 100. In addition modified Marshall scoring system was calculated according to objective and subjective findings of the patients prior to surgery and six months after radio-synovectomy. The highest evaluation score was 30 in modified Marshall scoring system where 19 points were provided by objective findings and 11 points were provided by subjective findings. Scores higher than 26 were defined as very good, between 21-25 was good, between 16-20 was medium, and values less than 16 points are considered to be poor. The obtained points using scoring systems were evaluated statistically. Results: the mean age was (31.7 ± 13.2) years. The average time period between the operation and radio-synovectomy was (12.8 ± 8.14) weeks. The calculated Lysholm scores prior to surgery, prior to radio-synovectomy and 6 months after radio-synovectomy were (38.8 ± 4.1), (60.0 ± 4.4) and (82.9 ± 6.5), respectively (p <0.001). Modified Marshall scores prior to surgery, and 6 months after radio-synovectomy, was (12.4 ± 2.7) and (25.5 ± 3.1) respectively (p <0.001). Conclusion

Relation between gamma-ray emission, radio bursts, and proton fluxes from solar flares

International Nuclear Information System (INIS)

Fomichev, V.V.; Chertok, I.M.

1985-01-01

Data on solar gamma-ray flares, including 24 flares with gamma-ray lines, recorded up to June 1982, are analyzed. It is shown that from the point of view of radio emission the differences between flares with and without gamma-ray lines has a purely quantitative character: the former are accompanied by the most intense microwave bursts. Meter type II bursts are not a distinctive feature of flares with gamma-ray lines. Pulsed flares, regardless of the presence or absence of gamma-ray lines, are not accompanied by significant proton fluxes at the earth. On the whole, contrary to the popular opinion in the literature, flares with gamma-ray lines do not display a deficit of proton flux in interplanetary space in comparison with similar flares without gamma-ray lines. The results of quantitative diagnostics of proton flares based on radio bursts are not at variance with the presence of flares without detectable gamma-ray emission in lines but with a pronounced increase in the proton flux at the earth. 23 references

Interpretation of the galactic radio-continuum and gamma-ray emission

International Nuclear Information System (INIS)

Beuermann, K.P.

1974-01-01

An analysis is performed of the nonthermal radio-continuum and gamma-ray emission of the galactic disc, using a spiral-arm model of the Galaxy. The results for the 408 MHz brightness temperature and the >100 MeV gamma-ray line intensity as a function of galactic longitude at bsup(II)=0 deg are presented. The observational implications, as well as the uncertainties in the calculations, are briefly discussed. An estimate of the possible range of the inverse Compton contribution to the observed gamma-ray flux is made

The Spectrum of Isotropic Diffuse Gamma-Ray Emission Between 100 Mev and 820 Gev

Science.gov (United States)

Ackermann, M.; Ajello, M.; Albert, A.; Atwood, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Brandt, T. J.; Hays, E.;

First Experimental Impulse-Radio Ultra-Wideband Transmission Under the Russian Spectral Emission Mask

DEFF Research Database (Denmark)

Grakhova, Elizaveta P.; Rommel, Simon; Jurado-Navas, Antonio

2016-01-01

Ultra-wideband impulse-radio wireless transmission under the stringent conditions and complex shape of the Russian spectral emission mask is experimentally demonstrated for the first time. Transmission of 1Gbit/s and 1.25Gbit/s signals over distances of 6m and 3m is achieved with a BER below 3.8×10-3....

Spectral Energy Distribution and Radio Halo of NGC 253 at Low Radio Frequencies

Energy Technology Data Exchange (ETDEWEB)

Kapińska, A. D.; Staveley-Smith, L.; Meurer, G. R.; For, B.-Q. [International Centre for Radio Astronomy Research (ICRAR), University of Western Australia, 35 Stirling Hwy, WA 6009 (Australia); Crocker, R. [Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia); Bhandari, S.; Callingham, J. R.; Gaensler, B. M.; Hancock, P. J.; Lenc, E. [ARC Centre of Excellence for All-Sky Astrophysics (CAASTRO), Sydney NSW (Australia); Hurley-Walker, N.; Seymour, N. [International Centre for Radio Astronomy Research (ICRAR), Curtin University, Bentley, WA 6102 (Australia); Offringa, A. R. [Netherlands Institute for Radio Astronomy (ASTRON), P.O. Box 2, 7990 AA Dwingeloo (Netherlands); Hanish, D. J. [Spitzer Science Center, California Institute of Technology, MC 220-6, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Ekers, R. D.; Bell, M. E. [CSIRO Astronomy and Space Science (CASS), P.O. Box 76, Epping, NSW 1710 (Australia); Dwarakanath, K. S. [Raman Research Institute, Bangalore 560080 (India); Hindson, L. [Centre of Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB (United Kingdom); Johnston-Hollitt, M. [School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington 6140 (New Zealand); McKinley, B., E-mail: anna.kapinska@uwa.edu.au [School of Physics, The University of Melbourne, Parkville, VIC 3010 (Australia); and others

2017-03-20

We present new radio continuum observations of NGC 253 from the Murchison Widefield Array at frequencies between 76 and 227 MHz. We model the broadband radio spectral energy distribution for the total flux density of NGC 253 between 76 MHz and 11 GHz. The spectrum is best described as a sum of a central starburst and extended emission. The central component, corresponding to the inner 500 pc of the starburst region of the galaxy, is best modeled as an internally free–free absorbed synchrotron plasma, with a turnover frequency around 230 MHz. The extended emission component of the spectrum of NGC 253 is best described as a synchrotron emission flattening at low radio frequencies. We find that 34% of the extended emission (outside the central starburst region) at 1 GHz becomes partially absorbed at low radio frequencies. Most of this flattening occurs in the western region of the southeast halo, and may be indicative of synchrotron self-absorption of shock-reaccelerated electrons or an intrinsic low-energy cutoff of the electron distribution. Furthermore, we detect the large-scale synchrotron radio halo of NGC 253 in our radio images. At 154–231 MHz the halo displays the well known X-shaped/horn-like structure, and extends out to ∼8 kpc in the z -direction (from the major axis).

Star Formation Rates in Lyman Break Galaxies: Radio Stacking of LBGs in the COSMOS Field and the Sub-μJy Radio Source Population

Science.gov (United States)

Carilli, C. L.; Lee, Nicholas; Capak, P.; Schinnerer, E.; Lee, K.-S.; McCraken, H.; Yun, M. S.; Scoville, N.; Smolčić, V.; Giavalisco, M.; Datta, A.; Taniguchi, Y.; Urry, C. Megan

2008-12-01

We present an analysis of the radio properties of large samples of Lyman break galaxies (LBGs) at z ~ 3, 4, and 5 from the COSMOS field. The median stacking analysis yields a statistical detection of the z ~ 3 LBGs (U-band dropouts), with a 1.4 GHz flux density of 0.90 +/- 0.21 μJy. The stacked emission is unresolved, with a size = 3 is smaller than at lower redshifts. Conversely, the radio luminosity for a given star formation rate may be systematically lower at very high redshift. Two possible causes for a suppressed radio luminosity are (1) increased inverse Compton cooling of the relativistic electron population due to scattering off the increasing CMB at high redshift or (2) cosmic-ray diffusion from systematically smaller galaxies. The radio detections of individual sources are consistent with a radio-loud AGN fraction of 0.3%. One source is identified as a very dusty, extreme starburst galaxy (a "submillimeter galaxy"). Based on observations in the COSMOS Legacy Survey including those taken on the HST, Keck, NRAO-VLA, Subaru, KPNO 4 m, CTIO 4 m, and CFHT 3.6 m. The Very Large Array of the National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

POWERFUL RADIO EMISSION FROM LOW-MASS SUPERMASSIVE BLACK HOLES FAVORS DISK-LIKE BULGES

Energy Technology Data Exchange (ETDEWEB)

Wang, J.; Xu, Y.; Xu, D. W.; Wei, J. Y., E-mail: wj@bao.ac.cn [CAS Key Laboratory of Space Astronomy and Technology, National Astronomical Observatories, Chinese Academy of Sciences, Beijing (China)

2016-12-10

The origin of spin of low-mass supermassive black holes (SMBHs) is still a puzzle at present. We report here a study on the host galaxies of a sample of radio-selected nearby ( z < 0.05) Seyfert 2 galaxies with a BH mass of 10{sup 6–7} M{sub ⊙}. By modeling the SDSS r -band images of these galaxies through a two-dimensional bulge+disk decomposition, we identify a new dependence of SMBH's radio power on host bulge surface brightness profiles, in which more powerful radio emission comes from an SMBH associated with a more disk-like bulge. This result means low-mass and high-mass SMBHs are spun up by two entirely different modes that correspond to two different evolutionary paths. A low-mass SMBH is spun up by a gas accretion with significant disk-like rotational dynamics of the host galaxy in the secular evolution, while a high-mass one by a BH–BH merger in the merger evolution.

Fibre structure of decametric type II radio bursts as a manifestation of emission propagation effects in a disturbed near-solar plasma

Directory of Open Access Journals (Sweden)

A. N. Afanasiev

2009-10-01

Full Text Available This paper addresses the fine structure of solar decametric type II radio bursts in the form of drifting narrowband fibres on the dynamic spectrum. Observations show that this structure appears in those events where there is a coronal mass ejection (CME traveling in the near-solar space ahead of the shock wave responsible for the radio burst. The diversity in observed morphology of fibres and values of their parameters implies that the fibres may be caused by different formation mechanisms. The burst emission propagates through extremely inhomogeneous plasma of the CME, so one possible mechanism can be related to radio propagation effects. I suggest that the fibres in some events represent traces of radio emission caustics, which are formed due to regular refraction of radio waves on the large-scale inhomogeneous structure of the CME front. To support this hypothesis, I have modeled the propagation of radio waves through inhomogeneous plasma of the CME, taking into consideration the presence of electron density fluctuations in it. The calculations, which are based on the Monte Carlo technique, indicate that, in particular, the emission of the fibres should be harmonic. Moreover, the mechanism under consideration suggests that in solar observations from two different points in space, the observed sets of fibres can be shifted in frequency with respect to one another or can have a different structure. This potentially can be used for identifying fibres caused by the propagation effects.

Directivity of the radio emission from the K1 dwarf star AB Doradus

Science.gov (United States)

Lim, Jeremy; White, Stephen M.; Nelson, Graam J.; Benz, Arnold O.

1994-01-01

We present measurements of the spectrum and polarization of the flaring radio emission from the K1 dwarf star AB Doradus, together with previously reported single frequency measurements (with no polarization information) on 3 other days. On all 4 days spanning a 6 month period, the emission was strong and, when folded with the stellar rotation period, showed similar time variations with two prominant peaks at phase 0.35 and 0.75. These peaks coincide in longitude with two large starspots identified from the stellar optical light curve and have half-powe widths as small as 0.1 rotations and no larger than 0.2 rotations. The modulated emission shows no measurable circular polarization, and its two peaks have different turnover frequencies.

Observations of radio emission in the 18 cm hydroxyl lines in the direction of Herbig-Haro objects and reflection nebulae

International Nuclear Information System (INIS)

Pashchenko, M.I.; Rudnitskij, G.M.

1980-01-01

In 1978 observations of Herbig-Haro objects and R associations in the 1665 and 1667 MHz main lines of the ground state of the OH molecule have been carried out at the Large radio telescope of the Nancay Radio Astronomy Station (France). Out of the 63 objects searched, the OH emission has been observed in 36 directions. In most cases, the observed line profiles have a simple singlepeak structure, with the line widths of 1-3 km/s. This emission most probably originates in interstellar dust clouds surrounding the Herbig-Haro objects and R associations. Some consequences of the results obtained are briefly discussed. Results of observations show that the quantity of strong maser radio sources near Herbig-Haro objects is not large

Relics in galaxy clusters at high radio frequencies

Science.gov (United States)

Kierdorf, M.; Beck, R.; Hoeft, M.; Klein, U.; van Weeren, R. J.; Forman, W. R.; Jones, C.

2017-04-01

Aims: We investigated the magnetic properties of radio relics located at the peripheries of galaxy clusters at high radio frequencies, where the emission is expected to be free of Faraday depolarization. The degree of polarization is a measure of the magnetic field compression and, hence, the Mach number. Polarization observations can also be used to confirm relic candidates. Methods: We observed three radio relics in galaxy clusters and one radio relic candidate at 4.85 and 8.35 GHz in total emission and linearly polarized emission with the Effelsberg 100-m telescope. In addition, we observed one radio relic candidate in X-rays with the Chandra telescope. We derived maps of polarization angle, polarization degree, and Faraday rotation measures. Results: The radio spectra of the integrated emission below 8.35 GHz can be well fitted by single power laws for all four relics. The flat spectra (spectral indices of 0.9 and 1.0) for the so-called Sausage relic in cluster CIZA J2242+53 and the so-called Toothbrush relic in cluster 1RXS 06+42 indicate that models describing the origin of relics have to include effects beyond the assumptions of diffuse shock acceleration. The spectra of the radio relics in ZwCl 0008+52 and in Abell 1612 are steep, as expected from weak shocks (Mach number ≈2.4). Polarization observations of radio relics offer a method of measuring the strength and geometry of the shock front. We find polarization degrees of more than 50% in the two prominent Mpc-sized radio relics, the Sausage and the Toothbrush, which are among the highest percentages of linear polarization detected in any extragalactic radio source to date. This is remarkable because the large beam size of the Effelsberg single-dish telescope corresponds to linear extensions of about 300 kpc at 8.35 GHz at the distances of the relics. The high degree of polarization indicates that the magnetic field vectors are almost perfectly aligned along the relic structure, as expected for shock

MURCHISON WIDEFIELD ARRAY LIMITS ON RADIO EMISSION FROM ANTARES NEUTRINO EVENTS

International Nuclear Information System (INIS)

Croft, S.; Kaplan, D. L.; Tingay, S. J.; Murphy, T.; Rowlinson, A.; Bell, M. E.; Adrián-Martínez, S.; Ardid, M.; Ageron, M.; Aubert, J.-J.; Albert, A.; André, M.; Anton, G.; Avgitas, T.; Baret, B.

2016-01-01

We present a search, using the Murchison Widefield Array (MWA), for electromagnetic (EM) counterparts to two candidate high-energy neutrino events detected by the ANTARES neutrino telescope in 2013 November and 2014 March. These events were selected by ANTARES because they are consistent, within 0.°4, with the locations of galaxies within 20 Mpc of Earth. Using MWA archival data at frequencies between 118 and 182 MHz, taken ∼20 days prior to, at the same time as, and up to a year after the neutrino triggers, we look for transient or strongly variable radio sources that are consistent with the neutrino positions. No such counterparts are detected, and we set a 5σ upper limit for low-frequency radio emission of ∼10 37 erg s −1 for progenitors at 20 Mpc. If the neutrino sources are instead not in nearby galaxies, but originate in binary neutron star coalescences, our limits place the progenitors at z ≳ 0.2. While it is possible, due to the high background from atmospheric neutrinos, that neither event is astrophysical, the MWA observations are nevertheless among the first to follow up neutrino candidates in the radio, and illustrate the promise of wide-field instruments like MWA for detecting EM counterparts to such events

MURCHISON WIDEFIELD ARRAY LIMITS ON RADIO EMISSION FROM ANTARES NEUTRINO EVENTS

Energy Technology Data Exchange (ETDEWEB)

Croft, S. [University of California, Berkeley, Astronomy Department, 501 Campbell Hall #3411, Berkeley, CA 94720 (United States); Kaplan, D. L. [Department of Physics, University of Wisconsin-Milwaukee, 1900 East Kenwood Boulevard, Milwaukee, WI 53211 (United States); Tingay, S. J. [International Centre for Radio Astronomy Research, Curtin University, Bentley, WA 6102 (Australia); Murphy, T.; Rowlinson, A. [ARC Centre of Excellence for All-sky Astrophysics (CAASTRO) (Australia); Bell, M. E. [CSIRO Australia Telescope National Facility, P.O. Box 76, Epping, NSW 1710 (Australia); Adrián-Martínez, S.; Ardid, M. [Institut d’Investigació per a la Gestió Integrada de les Zones Costaneres (IGIC)—Universitat Politècnica de València. C/ Paranimf 1, E-46730 Gandia (Spain); Ageron, M.; Aubert, J.-J. [Aix Marseille Université, CNRS/IN2P3, CPPM UMR 7346, F-13288, Marseille (France); Albert, A. [GRPHE—Université de Haute Alsace—Institut universitaire de technologie de Colmar, 34 rue du Grillenbreit BP 50568-68008 Colmar (France); André, M. [Technical University of Catalonia, Laboratory of Applied Bioacoustics, Rambla Exposició, E-08800 Vilanova i la Geltrú, Barcelona (Spain); Anton, G. [Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen Centre for Astroparticle Physics, Erwin-Rommel-Str. 1, D-91058 Erlangen (Germany); Avgitas, T.; Baret, B. [APC, Université Paris Diderot, CNRS/IN2P3, CEA/IRFU, Observatoire de Paris, Sorbonne Paris Cité, F-75205 Paris (France); Collaboration: for the MWA Collaboration; for the ANTARES Collaboration; for the TAROT Collaboration; for the ROTSE Collaboration; and others

2016-04-01

We present a search, using the Murchison Widefield Array (MWA), for electromagnetic (EM) counterparts to two candidate high-energy neutrino events detected by the ANTARES neutrino telescope in 2013 November and 2014 March. These events were selected by ANTARES because they are consistent, within 0.°4, with the locations of galaxies within 20 Mpc of Earth. Using MWA archival data at frequencies between 118 and 182 MHz, taken ∼20 days prior to, at the same time as, and up to a year after the neutrino triggers, we look for transient or strongly variable radio sources that are consistent with the neutrino positions. No such counterparts are detected, and we set a 5σ upper limit for low-frequency radio emission of ∼10{sup 37} erg s{sup −1} for progenitors at 20 Mpc. If the neutrino sources are instead not in nearby galaxies, but originate in binary neutron star coalescences, our limits place the progenitors at z ≳ 0.2. While it is possible, due to the high background from atmospheric neutrinos, that neither event is astrophysical, the MWA observations are nevertheless among the first to follow up neutrino candidates in the radio, and illustrate the promise of wide-field instruments like MWA for detecting EM counterparts to such events.

Curved Radio Spectra of Weak Cluster Shocks

Science.gov (United States)

Kang, Hyesung; Ryu, Dongsu

2015-08-01

In order to understand certain observed features of arc-like giant radio relics such as the rareness, uniform surface brightness, and curved integrated spectra, we explore a diffusive shock acceleration (DSA) model for radio relics in which a spherical shock impinges on a magnetized cloud containing fossil relativistic electrons. Toward this end, we perform DSA simulations of spherical shocks with the parameters relevant for the Sausage radio relic in cluster CIZA J2242.8+5301, and calculate the ensuing radio synchrotron emission from re-accelerated electrons. Three types of fossil electron populations are considered: a delta-function like population with the shock injection momentum, a power-law distribution, and a power law with an exponential cutoff. The surface brightness profile of the radio-emitting postshock region and the volume-integrated radio spectrum are calculated and compared with observations. We find that the observed width of the Sausage relic can be explained reasonably well by shocks with speed {u}{{s}}˜ 3× {10}3 {km} {{{s}}}-1 and sonic Mach number {M}{{s}}˜ 3. These shocks produce curved radio spectra that steepen gradually over (0.1-10){ν }{br} with a break frequency {ν }{br}˜ 1 GHz if the duration of electron acceleration is ˜60-80 Myr. However, the abrupt increase in the spectral index above ˜1.5 GHz observed in the Sausage relic seems to indicate that additional physical processes, other than radiative losses, operate for electrons with {γ }{{e}}≳ {10}4.

High-energy neutrinos from FR0 radio galaxies?

Science.gov (United States)

Tavecchio, F.; Righi, C.; Capetti, A.; Grandi, P.; Ghisellini, G.

2018-04-01

The sources responsible for the emission of high-energy (≳100 TeV) neutrinos detected by IceCube are still unknown. Among the possible candidates, active galactic nuclei with relativistic jets are often examined, since the outflowing plasma seems to offer the ideal environment to accelerate the required parent high-energy cosmic rays. The non-detection of single-point sources or - almost equivalently - the absence, in the IceCube events, of multiplets originating from the same sky position - constrains the cosmic density and the neutrino output of these sources, pointing to a numerous population of faint sources. Here we explore the possibility that FR0 radio galaxies, the population of compact sources recently identified in large radio and optical surveys and representing the bulk of radio-loud AGN population, can represent suitable candidates for neutrino emission. Modelling the spectral energy distribution of an FR0 radio galaxy recently associated with a γ-ray source detected by the Large Area Telescope onboard Fermi, we derive the physical parameters of its jet, in particular the power carried by it. We consider the possible mechanisms of neutrino production, concluding that pγ reactions in the jet between protons and ambient radiation is too inefficient to sustain the required output. We propose an alternative scenario, in which protons, accelerated in the jet, escape from it and diffuse in the host galaxy, producing neutrinos as a result of pp scattering with the interstellar gas, in strict analogy with the processes taking place in star-forming galaxies.

Fermi-LAT and Suzaku observations of the radio galaxy Centaurus B

International Nuclear Information System (INIS)

Katsuta, J.; Tanaka, Y. T.; Stawarz, Ł.; O’Sullivan, S. P.; Cheung, C. C.

2013-01-01

Centaurus B is a nearby radio galaxy positioned in the southern hemisphere close to the Galactic plane. Here, in this work, we present a detailed analysis of about 43 months of accumulated Fermi-LAT data of the γ-ray counterpart of the source initially reported in the 2nd Fermi-LAT catalog, and of newly acquired Suzaku X-ray data. We confirm its detection at GeV photon energies and analyze the extension and variability of the γ-ray source in the LAT dataset, in which it appears as a steady γ-ray emitter. The X-ray core of Centaurus B is detected as a bright source of a continuum radiation. We do not detect, however, any diffuse X-ray emission from the known radio lobes, with the provided upper limit only marginally consistent with the previously claimed ASCA flux. Two scenarios that connect the X-ray and γ-ray properties are considered. In the first one, we assume that the diffuse non-thermal X-ray emission component is not significantly below the derived Suzaku upper limit. In this case, modeling the inverse-Compton emission shows that the observed γ-ray flux of the source may in principle be produced within the lobes. This association would imply that efficient in-situ acceleration of the radiating electrons is occurring and that the lobes are dominated by the pressure from the relativistic particles. In the second scenario, with the diffuse X-ray emission well below the Suzaku upper limits, the lobes in the system are instead dominated by the magnetic pressure. In this case, the observed γ-ray flux is not likely to be produced within the lobes, but instead within the nuclear parts of the jet. In conclusion, by means of synchrotron self-Compton modeling, we show that this possibility could be consistent with the broad-band data collected for the unresolved core of Centaurus B, including the newly derived Suzaku spectrum.

X-RAYS FROM A RADIO-LOUD COMPACT BROAD ABSORPTION LINE QUASAR 1045+352 AND THE NATURE OF OUTFLOWS IN RADIO-LOUD BROAD ABSORPTION LINE QUASARS

International Nuclear Information System (INIS)

Kunert-Bajraszewska, Magdalena; Katarzynski, Krzysztof; Siemiginowska, Aneta; Janiuk, Agnieszka

2009-01-01

We present new results on X-ray properties of radio-loud broad absorption line (BAL) quasars and focus on broadband spectral properties of a high-ionization BAL (HiBAL) compact steep spectrum (CSS) radio-loud quasar 1045+352. This HiBAL quasar has a very complex radio morphology indicating either strong interactions between a radio jet and the surrounding interstellar medium or a possible re-start of the jet activity. We detected 1045+352 quasar in a short 5 ksec Chandra ACIS-S observation. We applied theoretical models to explain spectral energy distribution of 1045+352 and argue that non-thermal, inverse-Compton (IC) emission from the innermost parts of the radio jet can account for a large fraction of the observed X-ray emission. In our analysis, we also consider a scenario in which the observed X-ray emission from radio-loud BAL quasars can be a sum of IC jet X-ray emission and optically thin corona X-ray emission. We compiled a sample of radio-loud BAL quasars that were observed in X-rays to date and report no correlation between their X-ray and radio luminosity. However, the radio-loud BAL quasars show a large range of X-ray luminosities and absorption columns. This is consistent with the results obtained earlier for radio-quiet BAL quasars and may indicate an orientation effect in BAL quasars or more complex dependence between X-ray emission, radio emission, and an orientation based on the radio morphology.

A radio monitoring survey of ultra-luminous X-ray sources

Science.gov (United States)

Körding, E.; Colbert, E.; Falcke, H.

2005-06-01

We present the results of a radio monitoring campaign to search for radio emission from nearby ultra-luminous X-ray sources (ULXs). These sources are bright off-nuclear X-ray point sources with luminosities exceeding LX > 1039 erg s-1. A well-defined sample of the 9 nearest ULXs has been monitored eight times over 5 months with the Very Large Array in A and B configuration. Our limiting sensitivity is ≈0.15 mJy (4σ) for radio flares and ≈60 μJy for continuous emission. In M 82 two ULXs seem to have coincident compact radio sources, which are probably supernova remnants. No continuous or flaring radio emission has been detected from any other ULX. Thus, ULXs do not generally emit steady-state radio emission above radio powers of 1.5 × 1017 W/Hz. The non-detections of the continuous emission are consistent with beamed or unbeamed radio emission from accreting black holes of ≤ 103 M⊙ based on the radio/X-ray correlation. Other published radio detections (M 82, NGC 5408) are also discussed in this context. Both detections are significantly above our detection limit. If ULXs have flaring radio emission above 4 × 1017 W/Hz we can give an upper limit on the duty cycle of the flares of 6%. This upper limit is in agreement with the observed number of flares in Galactic radio transients. Additionally we present a yet unreported radio double structure in the nearby low-luminosity AGN NGC 4736.

Ohmic ion temperature and thermal diffusivity profiles from the JET neutron emission profile monitor

Energy Technology Data Exchange (ETDEWEB)

Esposito, B. (ENEA, Frascati (Italy). Centro Ricerche Energia); Marcus, F.B.; Conroy, S.; Jarvis, O.N.; Loughlin, M.J.; Sadler, G.; Belle, P. van (Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking); Adams, J.M.; Watkins, N. (AEA Industrial Technology, Harwell (United Kingdom))

1993-10-01

The JET neutron emission profile monitor was used to study ohmically heated deuterium discharges. The radial profile of the neutron emissivity is deduced from the line-integral data. The profiles of ion temperature, T[sub i], and ion thermal diffusivity, [chi][sub i], are derived under steady-state conditions. The ion thermal diffusivity is higher than, and its scaling with plasma current opposite to, that predicted by neoclassical theory. (author).

Ohmic ion temperature and thermal diffusivity profiles from the JET neutron emission profile monitor

International Nuclear Information System (INIS)

Esposito, B.

1993-01-01

The JET neutron emission profile monitor was used to study ohmically heated deuterium discharges. The radial profile of the neutron emissivity is deduced from the line-integral data. The profiles of ion temperature, T i , and ion thermal diffusivity, χ i , are derived under steady-state conditions. The ion thermal diffusivity is higher than, and its scaling with plasma current opposite to, that predicted by neoclassical theory. (author)

Analysis of Jovian decametric data: study of radio emission mechanisms

International Nuclear Information System (INIS)

Staelin, D.H.

1986-01-01

Catalogues of approx. 200 decametric arcs and approx. 200 gaps between arcs were studied, in an effort to reconcile the data with predictions for the model wherein reflections of Io-induced currents each emit in a conical pattern and yield a distinct radio arc. The most recent interpretations of this data suggest that these Io-produced Alfven waves persist for at least one or two passages of Io, and that the emission cone half angles are approx. 40 to 90 deg., varying from arc to arc. Below 1.2 MHz it was discovered that Jupiter emits radiation strongly modulated in frequency with periods of approx. 200 kHz; this quasi-sinusoidal emission (MSA) can shift more than 180 deg. in phase over periods of 6 seconds, although these shifts are usually much smaller. MSA is not strongly correlated with the longitudes of Io or Jupiter, and typically occurs in patches covering approx. 500 kHz or more for periods of a few minutes. Furthermore, this modulation sometimes resembles a train of impulses in frequency with exponential decays toward high frequencies. Comparison of these results with the previous studies of V-shaped S-bursts is suggestive of an emission mechanism

A Characterization of the Diffuse Galactic Emissions at Large Angular Scales Using the Tenerife Data

Directory of Open Access Journals (Sweden)

J. F. Macías-Pérez

2013-01-01

diffuse emission in the range from 20 to 60 GHz. To discriminate between different models of AME, low frequency microwave data from 10 to 20 GHz are needed. We present here a reanalysis of published and unpublished Tenerife data from 10 to 33 GHz at large angular scales (from 5 to 15 degrees. We cross-correlate the Tenerife data to templates of the main galactic diffuse emissions: synchrotron, free-free, and thermal dust. We find evidence of dust-correlated emission in the Tenerife data that could be explained as spinning dust grain emission.

The dust, nebular emission, and dependence on QSO radio properties of the associated Mg II absorption line systems

International Nuclear Information System (INIS)

Khare, Pushpa; Daniel, Vanden Berk; Rahmani, Hadi; York, Donald G.

2014-01-01

We studied dust reddening and [O II] emission in 1730 Mg II associated absorption systems (AAS; relative velocity with respect to QSOs, ≤3000 km s –1 ; in units of velocity of light, β, ≤0.01) with 0.4 ≤z abs ≤ 2 in the Sloan Digital Sky Survey DR7, focusing on their dependence on the radio and other QSO properties. We used control samples, several with matching radio properties, to show that (1) AAS in radio-detected (RD) QSOs cause 2.6 ± 0.2 times higher dust extinction than those in radio-undetected (RUD) ones, which in turn cause 2.9 ± 0.7 times the dust extinction in the intervening systems; (2) AAS in core-dominated QSOs cause 2.0 ± 0.1 times higher dust extinction than those in lobe-dominated QSOs; (3) the occurrence of AAS is 2.1 ± 0.2 times more likely in RD QSOs than in RUD QSOs and 1.8 ± 0.1 time more likely in QSOs having black holes with masses larger than 1.23 × 10 9 M ☉ than in those with lower-mass black holes; and (4) there is excess flux in [O II]λ3727 emission in the composite spectra of the AAS samples compared with those of the control samples, which is at the emission redshift. The presence of AAS enhances the O II emission from the active galactic nucleus and/or the host galaxy. This excess is similar for both RD and RUD samples and is 2.5 ± 0.4 times higher in lobe-dominated samples than in core-dominated samples. The excess depends on the black hole mass and Eddington ratio. All these point to the intrinsic nature of the AAS except for the systems with z abs > z em , which could be infalling galaxies.

Flattening and radio emission among elliptical galaxies

International Nuclear Information System (INIS)

Disney, M.J.; Sparks, W.B.; Wall, J.V.

1984-01-01

In a sample of 132 bright elliptical galaxies it is shown that there is a strong correlation between radio activity and flattening in the sense that radio ellipticals are both apparently and inherently rounder than the average elliptical. Both extended and compact sources are subject to the same correlation. No galaxies with axial ratios below 0.65 are found to be radio emitters. (author)

KILOPARSEC-SCALE JETS IN THREE RADIO-LOUD NARROW-LINE SEYFERT 1 GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Richards, Joseph L.; Lister, Matthew L., E-mail: jlr@purdue.edu [Department of Physics and Astronomy, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907 (United States)

2015-02-10

We have discovered kiloparsec-scale extended radio emission in three narrow-line Seyfert 1 galaxies (NLS1s) in sub-arcsecond resolution 9 GHz images from the Karl G. Jansky Very Large Array. We find all sources show two-sided, mildly core-dominated jet structures with diffuse lobes dominated by termination hotspots. These span 20–70 kpc with morphologies reminiscent of FR II radio galaxies, while the extended radio luminosities are intermediate between FR I and FR II sources. In two cases the structure is linear, while a 45° bend is apparent in the third. Very Long Baseline Array images at 7.6 GHz reveal parsec-scale jet structures, in two cases with extended structure aligned with the inner regions of the kiloparsec-scale jets. Based on this alignment, the ratio of the radio core–luminosity to the optical luminosity, the jet/counter-jet intensity and extension length ratios, and moderate core brightness temperatures (≲10{sup 10} K), we conclude these jets are mildly relativistic (β≲0.3, δ∼1−1.5) and aligned at moderately small angles to the line of sight (10–15°). The derived kinematic ages of ∼10{sup 6}–10{sup 7} yr are much younger than radio galaxies but comparable to other NLS1s. Our results increase the number of radio-loud NLS1s with known kiloparsec-scale extensions from 7 to 10 and suggest that such extended emission may be common, at least among the brightest of these sources.

Predicting radio fluxes of extrasolar planets (Griessmeier+, 2007)

NARCIS (Netherlands)

Griessmeier, J.M.; Zarka, P.; Spreeuw, H.

2007-01-01

Expected radio emission from presently known exoplanets. For each of the currently known exoplanets, we list its estimated magnetic moment, maximum radio emission frequency, plasma frequency in the ambient stellar wind, and radio fluxes according to three different models. (1 data file).

Particle reacceleration and apparent radio source structure

International Nuclear Information System (INIS)

Eilek, J.A.

1982-01-01

The radio galaxy model which uses magnetohydrodynamic turbulence generated by surface instabilities to reaccelerate the radiating electrons has striking consequences for apparent source structure. Strong wave damping in the plasma results in a narrow turbulent edge. Particles accelerated in this edge must diffuse across field lines into the radio source; this predicts strong limb brightening in some cases. The structure of this edge and diffusion into the source are described. The relevance of this model to jets, radio tails, and standard double sources is discussed

Radio-quiet Gamma-ray Pulsars

Directory of Open Access Journals (Sweden)

Lupin Chun-Che Lin

2016-09-01

Full Text Available A radio-quiet γ-ray pulsar is a neutron star that has significant γ-ray pulsation but without observed radio emission or only limited emission detected by high sensitivity radio surveys. The launch of the Fermi spacecraft in 2008 opened a new epoch to study the population of these pulsars. In the 2nd Fermi Large Area Telescope catalog of γ-ray pulsars, there are 35 (30 % of the 117 pulsars in the catalog known samples classified as radio-quiet γ-ray pulsars with radio flux density (S1400 of less than 30 μJy. Accompanying the observations obtained in various wavelengths, astronomers not only have the opportunity to study the emitting nature of radio-quiet γ-ray pulsars but also have proposed different models to explain their radiation mechanism. This article will review the history of the discovery, the emission properties, and the previous efforts to study pulsars in this population. Some particular cases known as Geminga-like pulsars (e.g., PSR J0633+1746, PSR J0007+7303, PSR J2021+4026, and so on are also to specified discuss their common and specific features.

The excess radio background and fast radio transients

International Nuclear Information System (INIS)

Kehayias, John; Kephart, Thomas W.; Weiler, Thomas J.

2015-01-01

In the last few years ARCADE 2, combined with older experiments, has detected an additional radio background, measured as a temperature and ranging in frequency from 22 MHz to 10 GHz, not accounted for by known radio sources and the cosmic microwave background. One type of source which has not been considered in the radio background is that of fast transients (those with event times much less than the observing time). We present a simple estimate, and a more detailed calculation, for the contribution of radio transients to the diffuse background. As a timely example, we estimate the contribution from the recently-discovered fast radio bursts (FRBs). Although their contribution is likely 6 or 7 orders of magnitude too small (though there are large uncertainties in FRB parameters) to account for the ARCADE 2 excess, our development is general and so can be applied to any fast transient sources, discovered or yet to be discovered. We estimate parameter values necessary for transient sources to noticeably contribute to the radio background

DISCOVERY OF ULTRA-STEEP SPECTRUM GIANT RADIO GALAXY WITH RECURRENT RADIO JET ACTIVITY IN ABELL 449

International Nuclear Information System (INIS)

Hunik, Dominika; Jamrozy, Marek

2016-01-01

We report a discovery of a 1.3 Mpc diffuse radio source with extremely steep spectrum fading radio structures in the vicinity of the Abell 449 cluster of galaxies. Its extended diffuse lobes are bright only at low radio frequencies and their synchrotron age is about 160 Myr. The parent galaxy of the extended relic structure, which is the dominant galaxy within the cluster, is starting a new jet activity. There are three weak X-rays sources in the vicinity of the cluster as found in the ROSAT survey, however it is not known if they are connected with this cluster of galaxies. Just a few radio galaxy relics are currently known in the literature, as finding them requires sensitive and high angular resolution low-frequency radio observations. Objects of this kind, which also are starting a new jet activity, are important for understanding the life cycle and evolution of active galactic nuclei. A new 613 MHz map as well as the archival radio data pertaining to this object are presented and analyzed

Diffuse γ-ray emission observed by the Fermi large area telescope: massive stars, cosmic rays and the census of the interstellar medium in the galaxy

International Nuclear Information System (INIS)

Tibaldo, L.

2011-01-01

Galactic diffuse γ-ray emission is produced by interactions of cosmic rays (CRs) with interstellar gas and low-energy radiation fields. This is the brightest component of the high-energy γ-ray sky, surveyed since 2008 with unprecedented sensitivity and angular resolution by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. Galactic diffuse emission constitutes not only a bright and structured background which needs to be modeled in order to study individual sources and fainter diffuse components, but it can be used also as a probe of the interstellar environment of the Milky Way. We present in-depth studies of LAT γ-ray observations of selected regions in the local and outer Galaxy. LAT data are compared with multiwavelength tracers of the interstellar medium (ISM), including radio/mm-wave lines of gas and infrared emission/extinction from dust. The impact of the HI optical depth, often overlooked in the past, is carefully examined and recognized currently as the dominant source of uncertainty in the interpretation of observations. On one hand, we discuss the constraints provided by the γ-ray data on the census of the interstellar gas. We determine the X C O = N(H 2 )/W C O ratio for several clouds, finding no significant gradients in the Galactic disc over a range of ∼ 3.5 kpc in Galactocentric radius, and variations of a factor ≤ 2 in nearby local clouds. We also find evidence for an ubiquitous dark phase of interstellar gas which does not shine at radio/mm wavelengths and which provides a mass ∼ 50% of that traced by CO. For the first time we determine its γ-ray spectrum which is found to be well correlated with that of HI, thus further confirming that the emission originates from interstellar gas. On the other hand, we use the emissivity per hydrogen atom to infer the distribution of CRs in distant locations not accessible by direct measurements. While the local HI emissivity is consistent with the CR spectra measured near

CO2 diffuse emission from maar lake: An example in Changbai volcanic field, NE China

Science.gov (United States)

Sun, Yutao; Guo, Zhengfu; Liu, Jiaqi; Du, Jianguo

2018-01-01

Numerous maars and monogenetic volcanic cones are distributed in northeast China, which are related to westward deep subduction of the Pacific Ocean lithosphere, comprising a significant part of the "Pacific Ring of Fire". It is well known that diffuse CO2 emissions from monogenetic volcanoes, including wet (e.g., maar lake) and dry degassing systems (e.g., soil diffuse emission, fault degassing, etc.), may contribute to budget of globally nature-derived greenhouse gases. However, their relationship between wet (e.g., maar lake) and concomitant dry degassing systems (e.g., soil diffuse emission, fault degassing, etc.) related to monogenetic volcanic field is poorly understood. Yuanchi maar, one of the typical monogenetic volcanic systems, is located on the eastern flank of Tianchi caldera in Changbai volcanic field of northeast China, which displays all of three forms of CO2 degassing including the maar lake, soil micro-seepage and fault degassing. Measurements of efflux of CO2 diffusion from the Yuanchi maar system (YMS) indicate that the average values of CO2 emissions from soil micro-seepage, fault degassing and water-air interface diffusion are 24.3 ± 23.3 g m- 2 d- 1, 39.2 ± 22.4 g m- 2 d- 1 and 2.4 ± 1.1 g m- 2 d- 1, respectively. The minimum output of CO2 diffuse emission from the YMS to the atmosphere is about 176.1 ± 88.3 ton/yr, of which 80.4% results from the dry degassing system. Degassing from the fault contributes to the most of CO2 emissions in all of the three forms of degassing in the YMS. Contributions of mantle, crust, air and organic CO2 to the soil gas are 0.01-0.10%, 10-20%, 32-36% and 48-54%, respectively, which are quantitatively constrained by a He-C isotope coupling calculation model. We propose that CO2 exsolves from the upper mantle melting beneath the Tianchi caldera, which migrates to the crustal magma chamber and further transports to the surface of YMS along the deep fault system. During the transportation processes, the emission

Hydroxylamine diffusion can enhance N₂O emissions in nitrifying biofilms: a modeling study.

Science.gov (United States)

Sabba, Fabrizio; Picioreanu, Cristian; Pérez, Julio; Nerenberg, Robert

2015-02-03

Wastewater treatment plants can be significant sources of nitrous oxide (N2O), a potent greenhouse gas. However, little is known about N2O emissions from biofilm processes. We adapted an existing suspended-growth mathematical model to explore N2O emissions from nitrifying biofilms. The model included N2O formation by ammonia-oxidizing bacteria (AOB) via the hydroxylamine and the nitrifier denitrification pathways. Our model suggested that N2O emissions from nitrifying biofilms could be significantly greater than from suspended growth systems under similar conditions. The main cause was the formation and diffusion of hydroxylamine, an AOB nitrification intermediate, from the aerobic to the anoxic regions of the biofilm. In the anoxic regions, hydroxylamine oxidation by AOB provided reducing equivalents used solely for nitrite reduction to N2O, since there was no competition with oxygen. For a continuous system, very high and very low dissolved oxygen (DO) concentrations resulted in lower emissions, while intermediate values led to higher emissions. Higher bulk ammonia concentrations and greater biofilm thicknesses increased emissions. The model effectively predicted N2O emissions from an actual pilot-scale granular sludge reactor for sidestream nitritation, but significantly underestimated the emissions when the NH2OH diffusion coefficient was assumed to be minimal. This numerical study suggests an unexpected and important role of hydroxylamine in N2O emission in biofilms.

VLA radio observations of AR Scorpii

Science.gov (United States)

Stanway, E. R.; Marsh, T. R.; Chote, P.; Gänsicke, B. T.; Steeghs, D.; Wheatley, P. J.

2018-03-01

Aims: AR Scorpii is unique amongst known white dwarf binaries in showing powerful pulsations extending to radio frequencies. Here we aim to investigate the multi-frequency radio emission of AR Sco in detail, in order to constrain its origin and emission mechanisms. Methods: We present interferometric radio frequency imaging of AR Sco at 1.5, 5 and 9 GHz, analysing the total flux and polarization behaviour of this source at high time resolution (10, 3 and 3 s), across a full 3.6 h orbital period in each band. Results: We find strong modulation of the radio flux on the orbital period and the orbital sideband of the white dwarf's spin period (also known as the "beat" period). This indicates that, like the optical flux, the radio flux arises predominantly from on or near the inner surface of the M-dwarf companion star. The beat-phase pulsations of AR Sco decrease in strength with decreasing frequency. They are strongest at 9 GHz and at an orbital phase 0.5. Unlike the optical emission from this source, radio emission from AR Sco shows weak linear polarization but very strong circular polarization, reaching 30% at an orbital phase 0.8. We infer the probable existence of a non-relativistic cyclotron emission component, which dominates at low radio frequencies. Given the required magnetic fields, this also likely arises from on or near the M-dwarf. A table of the flux time series is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/611/A66

Comparison of VLBI radio core and X-ray flux densities of extragalactic radio sources

International Nuclear Information System (INIS)

Bloom, S.D.; Marscher, A.P.

1990-01-01

The Einstein Observatory revealed that most quasars, selected in a variety of ways, are strong x-ray emitters. Radio bright quasars are statistically more luminous in the x-ray than their radio-quiet counterparts. It was also found that the 90 GHz to soft x-ray spectral index has a very small dispersion for sources selected by their strong millimeter emission. This implies a close relationship between compact radio flux density and x-ray emission. Strong correlations have been found between the arcsecond scale flux densities and soft x-ray fluxes. It is suggested that the correlation can be explained if the soft x-rays were produced by the synchrotron self-Compton (SSC) process within the compact radio emitting region. (author)

RELATIVISTIC PLASMA AS THE DOMINANT SOURCE OF THE OPTICAL CONTINUUM EMISSION IN THE BROAD-LINE RADIO GALAXY 3C 120

International Nuclear Information System (INIS)

Leon-Tavares, J.; Lobanov, A. P.; Arshakian, T. G.; Chavushyan, V. H.; Doroshenko, V. T.; Sergeev, S. G.; Efimov, Y. S.; Nazarov, S. V.

2010-01-01

We report a relation between radio emission in the inner jet of the Seyfert galaxy 3C 120 and optical continuum emission in this galaxy. Combining the optical variability data with multi-epoch high-resolution very long baseline interferometry observations reveals that an optical flare rises when a superluminal component emerges into the jet, and its maxima is related to the passage of such component through the location of a stationary feature at a distance of ∼1.3 pc from the jet origin. This indicates that a significant fraction of the optical continuum produced in 3C 120 is non-thermal, and it can ionize material in a sub-relativistic wind or outflow. We discuss implications of this finding for the ionization and structure of the broad emission line region, as well as for the use of broad emission lines for determining black hole masses in radio-loud active galactic nucleus.

Development of solar flares and features of the fine structure of solar radio emission

Science.gov (United States)

Chernov, G. P.; Fomichev, V. V.; Yan, Y.; Tan, B.; Tan, Ch.; Fu, Q.

2017-11-01

The reason for the occurrence of different elements of the fine structure of solar radio bursts in the decimeter and centimeter wavelength ranges has been determined based on all available data from terrestrial and satellite observations. In some phenomena, fast pulsations, a zebra structre, fiber bursts, and spikes have been observed almost simultaneously. Two phenomena have been selected to show that the pulsations of radio emission are caused by particles accelerated in the magnetic reconnection region and that the zebra structure is excited in a source, such as a magnetic trap for fast particles. The complex combination of unusual fiber bursts, zebra structure, and spikes in the phenomenon on December 1, 2004, is associated with a single source, a magnetic island formed after a coronal mass ejection.

Sporadic radio emission connected with a definite manifestation of solar activity in the near Earth space

Science.gov (United States)

Dudnic, A. V.; Zaljubovski, I. I.; Kartashev, V. M.; Shmatko, E. S.

1985-01-01

Sporadic radio emission of near Earth space at the frequency of 38 MHz is shown to appear in the event of a rapid development of instabilities in the ionospheric plasma. The instabilities are generated due to primary ionospheric disturbances occurring under the influence of solar chromospheric flares.

Detection and reduction of diffuse liquid and gas emissions in chemical and petrochemical industries; Ermittlung und Verminderung diffuser fluessiger und gasfoermiger Emissionen in der chemischen und petrochemischen Industrie

Energy Technology Data Exchange (ETDEWEB)

Koeppke, K.E. [Witten-Herdecke Univ. gGmbH, Witten (Germany). Inst. fuer Umwelttechnik und Management; Cuhls, C. [Halle-Wittenberg Univ., Halle (Germany). Inst. fuer Umwelttechnik

2002-09-01

In order to improve environmental protection, VOC emissions from diffuse sources are of growing importance. For the first time in Germany the present research report gives a detailed presentation of: constructive measures for the avoidance and reduction of diffuse emissions, adequate assembling procedures for equipments and installations, technical possibilities of leak detection and, different methods for the estimation of total emissions from chemical and petrochemical production plants. On the basis of own investigations and monitoring measures taken at various plants of chemical and petrochemical industries different measuring techniques for leak detection as well as methods for the estimation of total emissions from diffuse sources are analysed and their limits are described. (orig.)

THE SPECTACULAR RADIO-NEAR-IR-X-RAY JET OF 3C 111: THE X-RAY EMISSION MECHANISM AND JET KINEMATICS

Energy Technology Data Exchange (ETDEWEB)

Clautice, Devon; Perlman, Eric S. [Department of Physics and Space Sciences, Florida Institute of Technology, 150 W. University Boulevard, Melbourne, FL 32901 (United States); Georganopoulos, Markos [Department of Physics, University of Maryland—Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 (United States); Lister, Matthew L.; Hogan, Brandon [Department of Physics and Astronomy, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907 (United States); Tombesi, Francesco [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Cara, Mihai [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Marshall, Herman L. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Kazanas, Demos [NASA’s Goddard Space Flight Center, Astrophysics Science Division, Code 663, Greenbelt, MD 20771 (United States)

2016-08-01

Relativistic jets are the most energetic manifestation of the active galactic nucleus (AGN) phenomenon. AGN jets are observed from the radio through gamma-rays and carry copious amounts of matter and energy from the sub-parsec central regions out to the kiloparsec and often megaparsec scale galaxy and cluster environs. While most spatially resolved jets are seen in the radio, an increasing number have been discovered to emit in the optical/near-IR and/or X-ray bands. Here we discuss a spectacular example of this class, the 3C 111 jet, housed in one of the nearest, double-lobed FR II radio galaxies known. We discuss new, deep Chandra and Hubble Space Telescope ( HST ) observations that reveal both near-IR and X-ray emission from several components of the 3C 111 jet, as well as both the northern and southern hotspots. Important differences are seen between the morphologies in the radio, X-ray, and near-IR bands. The long (over 100 kpc on each side), straight nature of this jet makes it an excellent prototype for future, deep observations, as it is one of the longest such features seen in the radio, near-IR/optical, and X-ray bands. Several independent lines of evidence, including the X-ray and broadband spectral shape as well as the implied velocity of the approaching hotspot, lead us to strongly disfavor the EC/CMB model and instead favor a two-component synchrotron model to explain the observed X-ray emission for several jet components. Future observations with NuSTAR , HST , and Chandra will allow us to further constrain the emission mechanisms.

Soft X-ray emission from the radio pulsar PSR 0656 + 14

Science.gov (United States)

Cordova, F. A.; Middleditch, J.; Hjellming, R. M.; Mason, K. O.

1989-01-01

A radio source with a flux density of a few mJy was found in the error region of the soft X-ray source E0656 + 14, and identified as the radio pulsar PSR 0656 + 14. The radio source has a steep, nonthermal spectrum and a high degree of linear (62 percent) and circular (19 percent) polarization. The X-ray spectrum of the pulsar is among the softest sources observed with the Einstein Observatory. The X-ray data taken with the Einstein imaging proportional counter (IPC) permit a range of blackbody temperatures of 3-6 x 10 to the 5th K, and an equivalent column density of hydrogen smaller than 4 x 10 to the 20th/sq cm. If the assumption is made that the X-ray flux is thermal radiation from surface of the neutron star, then the pulsar must be at a distance smaller than 550 pc, consistent with the low dispersion measure of PSR 0656 + 14. The X-ray timing data suggest that the X-ray emission is modulated at the pulsar's 0.385-s spin period with an amplitude of 18 percent + or - 6 percent, and that there is a 0.0002 probability that this is spurious. It was noted that PSR 0656 + 14 is close to the geometric center of a 20-deg diameter soft X-ray emitting ring called the Gemini-Monoceros enhancement. The close distance of the pulsar, together with its relatively young age of 1.1 x 10 to the 5th yr, makes it possible that the ring is a supernova remnant from the explosion of the pulsar's progenitor. A radio source extending over a region 1.2 to 3.3 arcmin south of the pulsar is a candidate for association with the pulsar.

Soft X-ray emission from the radio pulsar PSR 0656 + 14

International Nuclear Information System (INIS)

Cordova, F.A.; Middleditch, J.; Hjellming, R.M.; Mason, K.O.

1989-01-01

A radio source with a flux density of a few mJy was found in the error region of the soft X-ray source E0656 + 14, and identified as the radio pulsar PSR 0656 + 14. The radio source has a steep, nonthermal spectrum and a high degree of linear (62%) and circular (19%) polarization. The X-ray spectrum of the pulsar is among the softest sources observed with the Einstein Observatory. The X-ray data taken with the Einstein imaging proportional counter (IPC) permit a range of blackbody temperatures of 3-6 x 10 to the 5th K, and an equivalent column density of hydrogen smaller than 4 x 10 to the 20th/sq cm. If the assumption is made that the X-ray flux is thermal radiation from surface of the neutron star, then the pulsar must be at a distance smaller than 550 pc, consistent with the low dispersion measure of PSR 0656 + 14. The X-ray timing data suggest that the X-ray emission is modulated at the pulsar's 0.385-s spin period with an amplitude of 18% + or - 6%, and that there is a 0.0002 probability that this is spurious. It was noted that PSR 0656 + 14 is close to the geometric center of a 20-deg diameter soft X-ray emitting ring called the Gemini-Monoceros enhancement. The close distance of the pulsar, together with its relatively young age of 1.1 x 10 to the 5th yr, makes it possible that the ring is a supernova remnant from the explosion of the pulsar's progenitor. A radio source extending over a region 1.2 to 3.3 arcmin south of the pulsar is a candidate for association with the pulsar. 46 refs

Fumarole/plume and diffuse CO2 emission from Sierra Negra volcano, Galapagos archipelago

Science.gov (United States)

Padron, E.; Hernandez Perez, P. A.; Perez, N.; Theofilos, T.; Melian, G.; Barrancos, J.; Virgil, G.; Sumino, H.; Notsu, K.

2009-12-01

The active shield-volcano Sierra Negra is part of the Galapagos hotspot. Sierra Negra is the largest shield volcano of Isabela Island, hosting a 10 km diameter caldera. Ten historic eruptions have occurred and some involved a frequently visited east caldera rim fissure zone called Volcan Chico. The last volcanic event occurred in October 2005 and lasted for about a week, covering approximately twenty percent of the eastern caldera floor. Sierra Negra volcano has experienced some significant changes in the chemical composition of its volcanic gas discharges after the 2005 eruption. This volcanic event produced an important SO2 degassing that depleted the magmatic content of this gas. Not significant changes in the MORB and plume-type helium contribution were observed after the 2005 eruption, with a 65.5 % of MORB and 35.5 % of plume contribution. In 2006 a visible and diffuse gas emission study was performed at the summit of Sierra Negra volcano, Galapagos, to evaluate degassing rate from this volcanic system. Diffuse degassing at Sierra Negra was mainly confined in three different DDS: Volcan Chico, the southern inner margin of the caldera, and Mina Azufral. These areas showed also visible degassing, which indicates highly fractured areas where volcano-hydrothermal fluids migrate towards surface. A total fumarole/plume SO2 emission of 11 ± 2 td-1 was calculated by mini-DOAS ground-based measurements at Mina Azufral fumarolic area. Molar ratios of major volcanic gas components were also measured in-situ at Mina Azufral with a portable multisensor. The results showed H2S/SO2, CO2/SO2 and H2O/SO2 molar ratios of 0.41, 52.2 and 867.9, respectively. Multiplying the observed SO2 emission rate times the observed (gas)i/SO2 mass ratio we have estimated other volatiles emission rates. The results showed that H2O, CO2 and H2S emission rates from Sierra Negra are 562, 394, and 2.4 t d-1, respectively. The estimated total output of diffuse CO2 emission from the summit of

Managing the Diffusion of Low Emission Vehicles

Energy Technology Data Exchange (ETDEWEB)

Van der Vooren, A.; Alkemade, F. [Innovation Studies Group, Copernicus Institute of Sustainable Development, Utrecht University, 3508TC Utrecht (Netherlands)

2012-03-13

There is significant uncertainty among technology providers, governments, and consumers about which technology will be the vehicle technology of the future. Governments try to stimulate the diffusion of low emission vehicles with diverse policy measures such as purchase price subsidies. However, the effect of such support measures on the speed and direction of technological change is unclear as different vehicle technologies might be preferred under different policy conditions. Decision makers, such as firm actors involved in green technology management, are thus strongly dependent on government policy when making strategic decisions. For these firm actors, determining their strategy regarding low emission vehicles is a complex task in a changing environment of coevolving consumer preferences, technology characteristics, and green technology policies. This paper presents an agent-based model of the competition between several emerging and market-ready low emission vehicle technologies and the dominant fossil-fuel-based internal combustion engine vehicles. The simulations illustrate the effects of different policy measures on technological change and their implications for the strategic actions of firm actors. More specifically, collaboration and standardization strategies can lead to synergies that contribute to technological change without risking early lock-in.

Fumarole/plume and diffuse CO2 emission from Sierra Negra caldera, Galapagos archipelago

Science.gov (United States)

Padrón, Eleazar; Hernández, Pedro A.; Pérez, Nemesio M.; Toulkeridis, Theofilos; Melián, Gladys; Barrancos, José; Virgili, Giorgio; Sumino, Hirochika; Notsu, Kenji

2012-08-01

Measurements of visible and diffuse gas emission were conducted in 2006 at the summit of Sierra Negra volcano, Galapagos, with the aim to better characterize degassing after the 2005 eruption. A total SO2 emission of 11 ± 2 t day-1 was derived from miniature differential optical absorption spectrometer (mini-DOAS) ground-based measurements of the plume emanating from the Mini Azufral fumarolic area, the most important site of visible degassing at Sierra Negra volcano. Using a portable multigas system, the H2S/SO2, CO2/SO2, and H2O/SO2 molar ratios in the Mina Azufral plume emissions were found to be 0.41, 52.2, and 867.9, respectively. The corresponding H2O, CO2, and H2S emission rates were 562, 394, and 3 t day-1, respectively. The total output of diffuse CO2 emissions from the summit of Sierra Negra volcano was 990 ± 85 t day-1, with 605 t day-1 being released by a deep source. The diffuse-to-plume CO2 emission ratio was about 1.5. Mina Azufral fumaroles released gasses containing 73.6 mol% of H2O; the main noncondensable components amounted to 97.4 mol% CO2, 1.5 mol% SO2, 0.6 mol% H2S, and 0.35 mol% N2. The higher H2S/SO2 ratio values found in 2006 as compared to those reported before the 2005 eruption reveal a significant hydrothermal contribution to the fumarolic emissions. 3He/4He ratios measured at Mina Azufral fumarolic discharges showed values of 17.88 ± 0.25 R A , indicating a mid-ocean ridge basalts (MORB) and a Galapagos plume contribution of 53 and 47 %, respectively.

The dust, nebular emission, and dependence on QSO radio properties of the associated Mg II absorption line systems

Energy Technology Data Exchange (ETDEWEB)

Khare, Pushpa [CSIR Emeritus Scientist, IUCAA, Ganeshkhind, Pune 411007 (India); Daniel, Vanden Berk [Physics Department, St. Vincent College, Latrobe, PA 15650 (United States); Rahmani, Hadi [School of Astronomy, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); York, Donald G., E-mail: pushpakhare@gmail.com [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States)

2014-10-10

We studied dust reddening and [O II] emission in 1730 Mg II associated absorption systems (AAS; relative velocity with respect to QSOs, ≤3000 km s{sup –1}; in units of velocity of light, β, ≤0.01) with 0.4 ≤z {sub abs} ≤ 2 in the Sloan Digital Sky Survey DR7, focusing on their dependence on the radio and other QSO properties. We used control samples, several with matching radio properties, to show that (1) AAS in radio-detected (RD) QSOs cause 2.6 ± 0.2 times higher dust extinction than those in radio-undetected (RUD) ones, which in turn cause 2.9 ± 0.7 times the dust extinction in the intervening systems; (2) AAS in core-dominated QSOs cause 2.0 ± 0.1 times higher dust extinction than those in lobe-dominated QSOs; (3) the occurrence of AAS is 2.1 ± 0.2 times more likely in RD QSOs than in RUD QSOs and 1.8 ± 0.1 time more likely in QSOs having black holes with masses larger than 1.23 × 10{sup 9} M {sub ☉} than in those with lower-mass black holes; and (4) there is excess flux in [O II]λ3727 emission in the composite spectra of the AAS samples compared with those of the control samples, which is at the emission redshift. The presence of AAS enhances the O II emission from the active galactic nucleus and/or the host galaxy. This excess is similar for both RD and RUD samples and is 2.5 ± 0.4 times higher in lobe-dominated samples than in core-dominated samples. The excess depends on the black hole mass and Eddington ratio. All these point to the intrinsic nature of the AAS except for the systems with z {sub abs} > z {sub em}, which could be infalling galaxies.

A Radio Emission Analysis of Classical Nova V351 Pup (1991)

Science.gov (United States)

Wendeln, Carolyn; Chomiuk, Laura; Finzell, Thomas; Linford, Justin D.; Strader, Jay

2017-05-01

Previously, Nova Puppis 1991 (V351 Pup) was measured to host one of the most massive ejections claimed in the literature. Multi-frequency radio detections from one epoch were published for this nova in the 1990's; and yet, the remaining data collected by the Karl G. Jansky Very Large Array (VLA) have remained unpublished. In this paper, we analyze the remaining unpublished data sets for V351 Pup at frequencies of 4.9, 8.4, 14.9, and 22.5 GHz. We fit the resulting light curve to a model of expanding thermal ejecta, under the assumption that the radio emission is dominated by free-free radiation and accounting for high levels of clumping in the ejecta. Images of V351 Pup in both the radio (from the VLA) and Hα+[N II] (from Hubble Space Telescope) exhibit no aspherical structure, strengthening our assumption of spherical symmetry. From expansion parallax methods, we estimate the distance to V351 Pup to be 5.0 ± 1.5 kpc. Our light-curve fit yields a value of {{log}}10({M}{ej})=-5.2+/- 0.7 {M}⊙ for the ejecta mass, implying that V351 Pup is on the low end of expectations for ejecta mass from classical novae. A comparison between our derived ejecta mass and theoretical models gives evidence for a very massive (1.25 {M}⊙ ) white dwarf, which is consistent with spectroscopic evidence for an oxygen-neon white dwarf.

The difference between radio-loud and radio-quiet active galaxies

Science.gov (United States)

Wilson, A. S.; Colbert, E. J. M.

1995-01-01

The recent development of unified theories of active galactic nuclei (AGNs) has indicated that there are two physically distinct classes of these objects--radio-loud and radio-quiet. Despite differences, the (probable) thermal emissions from the AGNs (continua and lines from X-ray to infrared wavelengths) are quite similar to the two classes of object. We argue that this last result suggests that the black hole masses and mass accretion rates in the two classes are not greatly different, and that the difference between the classes is associated with the spin of the black hole. We assume that the normal process of accretion through a disk does not lead to rapidly spinning holes and propose that galaxies (e.g., spirals) which have not suffered a recent major merger event contain nonrotating or only slowly rotating black holes. When two such galaxies merge, the two black holes are known to form a binary and we assume that they eventually coalesce. The ratio of the number of radio-loud to radio-quiet AGNs at a given thermal (e.g., optical) luminosity is determined by the galaxy merger rate. Comparisons between the predicted and observed radio luminosity functions constrain the efficiencies with which jet power is extracted from the spinning hole and radio emission is produced by the jet.

THE ROLE OF FAST MAGNETIC RECONNECTION ON THE RADIO AND GAMMA-RAY EMISSION FROM THE NUCLEAR REGIONS OF MICROQUASARS AND LOW LUMINOSITY AGNs

International Nuclear Information System (INIS)

Kadowaki, L. H. S.; Pino, E. M. de Gouveia Dal; Singh, C. B.

2015-01-01

Fast magnetic reconnection events can be a very powerful mechanism operating in the core region of microquasars and active galactic nuclei (AGNs). In earlier work, it has been suggested that the power released by fast reconnection events between the magnetic field lines lifting from the inner accretion disk region and the lines anchored into the central black hole could accelerate relativistic particles and produce the observed radio emission from microquasars and low luminosity AGNs (LLAGNs). Moreover, it has been proposed that the observed correlation between the radio emission and the mass of these sources, spanning 10 10 orders of magnitude in mass, might be related to this process. In the present work, we revisit this model comparing two different fast magnetic reconnection mechanisms, namely, fast reconnection driven by anomalous resistivity (AR) and by turbulence. We apply the scenario above to a much larger sample of sources (including also blazars, and gamma-ray bursts—GRBs), and find that LLAGNs and microquasars do confirm the trend above. Furthermore, when driven by turbulence, not only their radio but also their gamma-ray emission can be due to magnetic power released by fast reconnection, which may accelerate particles to relativistic velocities in the core region of these sources. Thus the turbulent-driven fast reconnection model is able to reproduce verywell the observed emission. On the other hand, the emission from blazars and GRBs does not follow the same trend as that of the LLAGNs and microquasars, indicating that the radio and gamma-ray emission in these cases is produced beyond the core, along the jet, by another population of relativistic particles, as expected

Direct estimation of diffuse gaseous emissions from coal fires: current methods and future directions

Science.gov (United States)

Engle, Mark A.; Olea, Ricardo A.; O'Keefe, Jennifer M. K.; Hower, James C.; Geboy, Nicholas J.

2013-01-01

Coal fires occur in nature spontaneously, contribute to increases in greenhouse gases, and emit atmospheric toxicants. Increasing interest in quantifying coal fire emissions has resulted in the adaptation and development of specialized approaches and adoption of numerical modeling techniques. Overview of these methods for direct estimation of diffuse gas emissions from coal fires is presented in this paper. Here we take advantage of stochastic Gaussian simulation to interpolate CO2 fluxes measured using a dynamic closed chamber at the Ruth Mullins coal fire in Perry County, Kentucky. This approach allows for preparing a map of diffuse gas emissions, one of the two primary ways that gases emanate from coal fires, and establishing the reliability of the study both locally and for the entire fire. Future research directions include continuous and automated sampling to improve quantification of gaseous coal fire emissions.

RADIO PROPERTIES OF THE BAT AGNs: THE FIR–RADIO RELATION, THE FUNDAMENTAL PLANE, AND THE MAIN SEQUENCE OF STAR FORMATION

Energy Technology Data Exchange (ETDEWEB)

Smith, Krista Lynne; Mushotzky, Richard F.; Vogel, Stuart; Shimizu, Thomas T. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Miller, Neal, E-mail: klsmith@astro.umd.edu [Department of Mathematics and Physics, Stevenson University, Stevenson, MD 21117 (United States)

2016-12-01

We conducted 22 GHz 1″ JVLA imaging of 70 radio-quiet active galactic nuclei (AGNs) from the Swift -BAT survey. We find radio cores in all but three objects. The radio morphologies of the sample fall into three groups: compact and core-dominated, extended, and jet-like. We spatially decompose each image into core flux and extended flux, and compare the extended radio emission with that predicted from previous Herschel observations using the canonical FIR–radio relation. After removing the AGN contribution to the FIR and radio flux densities, we find that the relation holds remarkably well despite the potentially different star formation physics in the circumnuclear environment. We also compare our core radio flux densities with predictions of coronal models and scale-invariant jet models for the origin of radio emission in radio-quiet AGNs, and find general consistency with both models. However, we find that the L {sub R}/ L {sub X} relation does not distinguish between star formation and non-relativistic AGN-driven outflows as the origin of radio emission in radio-quiet AGNs. Finally, we examine where objects with different radio morphologies fall in relation to the main sequence (MS) of star formation, and conclude that those AGNs that fall below the MS, as X-ray selected AGNs have been found to do, have core-dominated or jet-like 22 GHz morphologies.

Diffuse nesidioblastosis diagnosed on a Ga-68 DOTATATE positron emission tomography/computerized tomography

International Nuclear Information System (INIS)

Arun, Sasikumar; Mittal, Bhagwant Rai; Shukla, Jaya; Bhattacharya, Anish; Kumar, Praveen

2013-01-01

The authors describe a 50 days old pre-term infant with persistent hyperinsulinemic hypoglycemia of infancy in whom 68 Ga DOTATATE positron emission tomography/computerized tomography scan showed diffusely increased tracer uptake in the entire pancreas with no abnormal tracer uptake anywhere else in the body, suggestive of a diffuse variant of nesidioblastosis. (author)

Diffuse Helium Emission as a Precursory Sign of Volcanic Unrest

Science.gov (United States)

Padron, E.; Perez, N.; Hernandez Perez, P. A.; Sumino, H.; Melian Rodriguez, G.; Barrancos, J.; Nolasco, D.; Padilla, G.; Dionis, S.; Rodriguez, F.; Hernandez, I.; Calvo, D.; Peraza, M.; Nagao, K.

2012-12-01

Since July 16, 2011, an anomalous seismicity at El Hierro island, the youngest and smallest of the Canary Islands, was recorded by IGN seismic network. After the occurrence of more than 10,000 seismic events, volcanic tremor was recorded since 05:15 of the October 10, by all of the seismic stations on the island, with highest amplitudes recorded in the southernmost station. During the afternoon of October 12 a large light-green coloured area was observed in the sea to the souht of La Restinga village (at the southernmost part of El Hierro island), suggesting the existence of a submarine eruption. Since October 12, frequent episodes of, turbulent gas emission and foaming, and the appearance of steamy lava fragments has been observed on the sea surface. As part of the volcanic surveillance of the island, the Instituto Volcanologico de Canarias (INVOLCAN) geochemical monitoring program is carrying out diffuse helium surveys on the surface environment of El Hierro (soil atmosphere). This nobel gas has been investigated because it has been considered an almost ideal geochemical indicator because it is chemically inert, physically stable, nonbiogenic, sparingly soluble in water under ambient conditions and almost non-adsorbable. At each survey, 600 sampling sites covering the whole island and following an homogeneous distribution are selected for helium measurements in the soil gases, The helium concentration gradients with respect to its value on air (5.24 ppm) allow us to estimate a pure diffusive emission rate of helium throughout the island. The first survey was carried out on the summer of 2003, when the island was on a quiescence period. At this survey, the amount of helium released by the volcanic system of El Hierro was estimated in 6 kg/d. Since the beginning of the seismic unrest, 13 helium emission surveys have been carried out. The helium emission rate has shown an excellent agreement with the evolution of the volcanic crisis of the island, reaching 30 kg

Modeling diffuse phosphorus emissions to assist in best management practice designing

Science.gov (United States)

Kovacs, Adam; Zessner, Matthias; Honti, Mark; Clement, Adrienne

2010-05-01

A diffuse emission modeling tool has been developed, which is appropriate to support decision-making in watershed management. The PhosFate (Phosphorus Fate) tool allows planning best management practices (BMPs) in catchments and simulating their possible impacts on the phosphorus (P) loads. PhosFate is a simple fate model to calculate diffuse P emissions and their transport within a catchment. The model is a semi-empirical, catchment scale, distributed parameter and long-term (annual) average model. It has two main parts: (a) the emission and (b) the transport model. The main input data of the model are digital maps (elevation, soil types and landuse categories), statistical data (crop yields, animal numbers, fertilizer amounts and precipitation distribution) and point information (precipitation, meteorology, soil humus content, point source emissions and reservoir data). The emission model calculates the diffuse P emissions at their source. It computes the basic elements of the hydrology as well as the soil loss. The model determines the accumulated P surplus of the topsoil and distinguishes the dissolved and the particulate P forms. Emissions are calculated according to the different pathways (surface runoff, erosion and leaching). The main outputs are the spatial distribution (cell values) of the runoff components, the soil loss and the P emissions within the catchment. The transport model joins the independent cells based on the flow tree and it follows the further fate of emitted P from each cell to the catchment outlets. Surface runoff and P fluxes are accumulated along the tree and the field and in-stream retention of the particulate forms are computed. In case of base flow and subsurface P loads only the channel transport is taken into account due to the less known hydrogeological conditions. During the channel transport, point sources and reservoirs are also considered. Main results of the transport algorithm are the discharge, dissolved and sediment

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

GYRO-ORBIT SIZE, BRIGHTNESS TEMPERATURE LIMIT, AND IMPLAUSIBILITY OF COHERENT EMISSION BY BUNCHING IN SYNCHROTRON RADIO SOURCES

International Nuclear Information System (INIS)

Singal, Ashok K.

2012-01-01

We show that an upper limit on the maximum brightness temperature for a self-absorbed incoherent synchrotron radio source is obtained from the size of its gyro orbits, which in turn must lie well within the confines of the total source extent. These temperature limits are obtained without recourse to inverse Compton effects or the condition of equipartition of energy between magnetic fields and relativistic particles. For radio variables, the intra-day variability implies brightness temperatures ∼10 19 K in the comoving rest frame of the source. This, if interpreted purely due to an incoherent synchrotron emission, would imply gyroradii >10 28 cm, the size of the universe, while from the causality arguments the inferred maximum size of the source in such a case is ∼ 15 cm. Such high brightness temperatures are sometimes modeled in the literature as some coherent emission process where bunches of non-thermal particles are somehow formed that radiate in phase. We show that, unlike in the case of curvature radiation models proposed in pulsars, in the synchrotron radiation mechanism the oppositely charged particles would contribute together to the coherent phenomenon without the need to form separate bunches of the opposite charges. At the same time we show that bunches would disperse over dimensions larger than a wavelength in time shorter than the gyro orbital period (∼< 0.1 s). Therefore, a coherent emission by bunches cannot be a plausible explanation of the high brightness temperatures inferred in extragalactic radio sources showing variability over a few hours or longer.

Origin of solar radio waves

International Nuclear Information System (INIS)

Olmr, J.

1977-01-01

Solar radiowave radiation amounts to about 10 -7 of the total solar radiation. The solar atmosphere emits radiation of different wavelengths from a fraction of nanometer to kilometer waves. The solar radiowaves are of thermal origin and except for neutral hydrogen emission and solid body radio emission their emission always results from free electrons. The radiowave radiation active components were classified in several types, such as noise storms, flashes, flares, continuum, and flashes lasting for several minutes. The respective types are discussed and their origins shown. The mechanisms are described permitting the formation of radio waves of nonthermal origin, i.e., plasma oscillations, gyromagnetic emission, synchrotron and Cherenkov radiations. (J.P.)

Spectrum of the isotropic diffuse gamma-ray emission derived from first-year Fermi Large Area Telescope data.

Science.gov (United States)

Abdo, A A; Ackermann, M; Ajello, M; Atwood, W B; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cavazzuti, E; Cecchi, C; Celik, O; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Cominsky, L R; Conrad, J; Cutini, S; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; Di Bernardo, G; do Couto e Silva, E; Drell, P S; Drlica-Wagner, A; Dubois, R; Dumora, D; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Fortin, P; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gaggero, D; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giommi, P; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guillemot, L; Guiriec, S; Gustafsson, M; Hanabata, Y; Harding, A K; Hayashida, M; Hughes, R E; Itoh, R; Jackson, M S; Jóhannesson, G; Johnson, A S; Johnson, R P; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; Kuehn, F; Kuss, M; Lande, J; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Mazziotta, M N; McConville, W; McEnery, J E; Meurer, C; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Omodei, N; Orlando, E; Ormes, J F; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Porter, T A; Rainò, S; Rando, R; Razzano, M; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Rochester, L S; Rodriguez, A Y; Roth, M; Ryde, F; Sadrozinski, H F-W; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Sellerholm, A; Sgrò, C; Shaw, M S; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Starck, J-L; Strickman, M S; Strong, A W; Suson, D J; Tajima, H; Takahashi, H; Takahashi, T; Tanaka, T; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Uchiyama, Y; Usher, T L; Vasileiou, V; Vilchez, N; Vitale, V; Waite, A P; Wang, P; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M

2010-03-12

We report on the first Fermi Large Area Telescope (LAT) measurements of the so-called "extragalactic" diffuse gamma-ray emission (EGB). This component of the diffuse gamma-ray emission is generally considered to have an isotropic or nearly isotropic distribution on the sky with diverse contributions discussed in the literature. The derivation of the EGB is based on detailed modeling of the bright foreground diffuse Galactic gamma-ray emission, the detected LAT sources, and the solar gamma-ray emission. We find the spectrum of the EGB is consistent with a power law with a differential spectral index gamma = 2.41 +/- 0.05 and intensity I(>100 MeV) = (1.03 +/- 0.17) x 10(-5) cm(-2) s(-1) sr(-1), where the error is systematics dominated. Our EGB spectrum is featureless, less intense, and softer than that derived from EGRET data.

Energetic electron propagation in the decay phase of non-thermal flare emission

Energy Technology Data Exchange (ETDEWEB)

Huang, Jing; Yan, Yihua [Key Laboratory of Solar Activities, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Tsap, Yuri T., E-mail: huangj@nao.cas.cn [Crimean Astrophysical Observatory of Kyiv National Taras Shevchenko University, 98409 Crimea, Nauchny (Ukraine)

2014-06-01

On the basis of the trap-plus-precipitation model, the peculiarities of non-thermal emission in the decay phase of solar flares have been considered. The calculation formulas for the escape rate of trapped electrons into the loss cone in terms of time profiles of hard X-ray (HXR) and microwave (MW) emission have been obtained. It has been found that the evolution of the spectral indices of non-thermal emission depend on the regimes of the pitch angle diffusion of trapped particles into the loss cone. The properties of non-thermal electrons related to the HXR and MW emission of the solar flare on 2004 November 3 are studied with Nobeyama Radioheliograph, Nobeyama Radio Polarimeters, RHESSI, and Geostationary Operational Environmental Satellite observations. The spectral indices of non-thermal electrons related to MW and HXR emission remained constant or decreased, while the MW escape rate as distinguished from that of the HXRs increased. This may be associated with different diffusion regimes of trapped electrons into the loss cone. New arguments in favor of an important role of the superstrong diffusion for high-energy electrons in flare coronal loops have been obtained.

Analytic calculation of radio emission from parametrized extensive air showers: A tool to extract shower parameters

Science.gov (United States)

Scholten, O.; Trinh, T. N. G.; de Vries, K. D.; Hare, B. M.

2018-01-01

The radio intensity and polarization footprint of a cosmic-ray induced extensive air shower is determined by the time-dependent structure of the current distribution residing in the plasma cloud at the shower front. In turn, the time dependence of the integrated charge-current distribution in the plasma cloud, the longitudinal shower structure, is determined by interesting physics which one would like to extract, such as the location and multiplicity of the primary cosmic-ray collision or the values of electric fields in the atmosphere during thunderstorms. To extract the structure of a shower from its footprint requires solving a complicated inverse problem. For this purpose we have developed a code that semianalytically calculates the radio footprint of an extensive air shower given an arbitrary longitudinal structure. This code can be used in an optimization procedure to extract the optimal longitudinal shower structure given a radio footprint. On the basis of air-shower universality we propose a simple parametrization of the structure of the plasma cloud. This parametrization is based on the results of Monte Carlo shower simulations. Deriving the parametrization also teaches which aspects of the plasma cloud are important for understanding the features seen in the radio-emission footprint. The calculated radio footprints are compared with microscopic CoREAS simulations.

Radio-Frequency Emissions from Streamer Collisions: Implications for High-Energy Processes.

Science.gov (United States)

Luque, A.

2017-12-01

The production of energetic particles in a discharge corona is possibly linked to the collision of streamers of opposite polarities [Cooray et al. (2009), Kochkin et al. (2012), Østgaard et al. (2016)]. There is also experimental evidence linking it to radio-frequency emissions in the UHF frequency range (300 MHz-3 GHz) [Montanyà et al. (2015), Petersen and Beasley (2014)]. Here we investigate these two links by modeling the radio-frequency emissions emanating from an encounter between two counter-propagating streamers. Our numerical model combines self-consistently a conservative, high-order Finite-Volume scheme for electron transport with a Finite-Difference Time-Domain (FDTD) method for electromagnetic propagation. We also include the most relevant reactions for streamer propagation: impact ionization, dissociative attachment and photo-ionization. Our implementation benefits from massive parallelization by running on a General-Purpose Graphical Processing Unit (GPGPU). With this code we found that streamer encounters emit electromagnetic waves predominantly in the UHF range, supporting the hypothesis that streamer collisions are essential precursors of high-energy processes in electric discharges. References Cooray, V., et al., J. Atm. Sol.-Terr. Phys., 71, 1890, doi:10.1016/j.jastp.2009.07.010 (2009). Kochkin, P. O., et al., J. Phys. D, 45, 425202, doi: 10.1088/0022-3727/45/42/425202 (2012). Montanyà, J., et al., J. Atm. Sol.-Terr. Phys., 136, 94, doi:10.1016/j.jastp.2015.06.009, (2015). Østgaard, N., et al., J. Geophys. Res. (Atmos.), 121, 2939, doi:10.1002/2015JD024394 (2016). Petersen, D., and W. Beasley, Atmospheric Research, 135, 314, doi:10.1016/j.atmosres.2013.02.006 (2014).

Identification of a Likely Radio Counterpart to the Rapid Burster

Science.gov (United States)

Moore, Christopher B.; Rutledge, Robert E.; Fox, Derek W.; Guerriero, Robert A.; Lewin, Walter H. G.; Fender, Robert; van Paradijs, Jan

2000-04-01

We have identified a likely radio counterpart to the low-mass X-ray binary MXB 1730-335 (the Rapid Burster). The counterpart has shown 8.4 GHz radio on/off behavior correlated with the X-ray on/off behavior as observed by the RXTE/ASM during six VLA observations. The probability of an unrelated, randomly varying background source duplicating this behavior is 1%-3% depending on the correlation timescale. The location of the radio source is R.A. 17h33m24.61s, decl. -33 deg23'19.8" (J2000), +/-0.1". We do not detect 8.4 GHz radio emission coincident with type II (accretion-driven) X-ray bursts. The ratio of radio to X-ray emission during such bursts is constrained to be below the ratio observed during X-ray-persistent emission at the 2.9 σ level. Synchrotron bubble models of the radio emission can provide a reasonable fit to the full data set, collected over several outbursts, assuming that the radio evolution is the same from outburst to outburst but given the physical constraints the emission is more likely to be due to ~1 hr radio flares such as have been observed from the X-ray binary GRS 1915+105.

J1649+2635: A Grand-Design Spiral with a Large Double-Lobed Radio Source

Science.gov (United States)

Mao, Minnie Y.; Owen, Frazer; Duffin, Ryan; Keel, Bill; Lacy, Mark; Momjian, Emmanuel; Morrison, Glenn; Mroczkowski, Tony; Neff, Susan; Norris, Ray P.;

UPPER LIMITS ON PULSED RADIO EMISSION FROM THE 6.85 s X-RAY PULSAR XTE J0103-728 IN THE SMALL MAGELLANIC CLOUD

International Nuclear Information System (INIS)

Crawford, Fronefield; Devour, Brian M.; Takacs, Brian P.; Lorimer, Duncan R.; Kondratiev, Vladislav I.

2009-01-01

X-ray pulsations with a 6.85 s period were recently detected in the Small Magellanic Cloud (SMC) and were subsequently identified as originating from the Be/X-ray binary system XTE J0103-728. The recent localization of the source of the X-ray emission has made a targeted search for radio pulsations from this source possible. The detection of pulsed radio emission from XTE J0103-728 would make it only the second system after PSR B1259-63 that is both a Be/X-ray binary and a radio pulsar. We observed XTE J0103-728 in 2008 February with the Parkes 64 m radio telescope soon after the identification of the source of X-ray pulsations was reported in order to search for corresponding radio pulsations. We used a continuous 6.4 hr observation with a 256 MHz bandwidth centered at 1390 MHz using the center beam of the Parkes multibeam receiver. In the subsequent data analysis, which included a folding search, a Fourier search, a fast-folding algorithm search, and a single pulse search, no pulsed signals were found for trial dispersion measures (DMs) between 0 and 800 pc cm -3 . This DM range easily encompasses the expected values for sources in the SMC. We place an upper limit of ∼45 mJy kpc 2 on the luminosity of periodic radio emission from XTE J0103-728 at the epoch of our observation, and we compare this limit to a range of luminosities measured for PSR B1259-63, the only Be/X-ray binary currently known to emit radio pulses. We also compare our limit to the radio luminosities of neutron stars having similarly long spin periods to XTE J0103-728. Since the radio pulses from PSR B1259-63 are eclipsed and undetectable during the portion of the orbit near periastron, repeated additional radio search observations of XTE J0103-728 may be valuable if it is undergoing similar eclipsing and if such observations are able to sample the orbital phase of this system well.

The isotropic radio background revisited

Energy Technology Data Exchange (ETDEWEB)

Fornengo, Nicolao; Regis, Marco [Dipartimento di Fisica Teorica, Università di Torino, via P. Giuria 1, I–10125 Torino (Italy); Lineros, Roberto A. [Instituto de Física Corpuscular – CSIC/U. Valencia, Parc Científic, calle Catedrático José Beltrán, 2, E-46980 Paterna (Spain); Taoso, Marco, E-mail: fornengo@to.infn.it, E-mail: rlineros@ific.uv.es, E-mail: regis@to.infn.it, E-mail: taoso@cea.fr [Institut de Physique Théorique, CEA/Saclay, F-91191 Gif-sur-Yvette Cédex (France)

2014-04-01

We present an extensive analysis on the determination of the isotropic radio background. We consider six different radio maps, ranging from 22 MHz to 2.3 GHz and covering a large fraction of the sky. The large scale emission is modeled as a linear combination of an isotropic component plus the Galactic synchrotron radiation and thermal bremsstrahlung. Point-like and extended sources are either masked or accounted for by means of a template. We find a robust estimate of the isotropic radio background, with limited scatter among different Galactic models. The level of the isotropic background lies significantly above the contribution obtained by integrating the number counts of observed extragalactic sources. Since the isotropic component dominates at high latitudes, thus making the profile of the total emission flat, a Galactic origin for such excess appears unlikely. We conclude that, unless a systematic offset is present in the maps, and provided that our current understanding of the Galactic synchrotron emission is reasonable, extragalactic sources well below the current experimental threshold seem to account for the majority of the brightness of the extragalactic radio sky.

The isotropic radio background revisited

International Nuclear Information System (INIS)

Fornengo, Nicolao; Regis, Marco; Lineros, Roberto A.; Taoso, Marco

2014-01-01

We present an extensive analysis on the determination of the isotropic radio background. We consider six different radio maps, ranging from 22 MHz to 2.3 GHz and covering a large fraction of the sky. The large scale emission is modeled as a linear combination of an isotropic component plus the Galactic synchrotron radiation and thermal bremsstrahlung. Point-like and extended sources are either masked or accounted for by means of a template. We find a robust estimate of the isotropic radio background, with limited scatter among different Galactic models. The level of the isotropic background lies significantly above the contribution obtained by integrating the number counts of observed extragalactic sources. Since the isotropic component dominates at high latitudes, thus making the profile of the total emission flat, a Galactic origin for such excess appears unlikely. We conclude that, unless a systematic offset is present in the maps, and provided that our current understanding of the Galactic synchrotron emission is reasonable, extragalactic sources well below the current experimental threshold seem to account for the majority of the brightness of the extragalactic radio sky

Radio Flares from Gamma-ray Bursts

Science.gov (United States)

Kopač, D.; Mundell, C. G.; Kobayashi, S.; Virgili, F. J.; Harrison, R.; Japelj, J.; Guidorzi, C.; Melandri, A.; Gomboc, A.

2015-06-01

We present predictions of centimeter and millimeter radio emission from reverse shocks (RSs) in the early afterglows of gamma-ray bursts (GRBs) 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 parameterization 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. and Melandri et al. in which the typical frequency of the RS was suggested to lie at radio rather than optical wavelengths at early times, we show that the brightest and most distinct RS 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 optical peaks, high isotropic energies, lower circumburst medium densities, and at observing frequencies that are less prone to synchrotron self-absorption effects—typically above a few GHz. Given recent detections of polarized prompt gamma-ray and optical RS emission, we suggest that detection of polarized radio/millimeter emission will unambiguously confirm the presence of low-frequency RSs at early time.

RADIO FLARES FROM GAMMA-RAY BURSTS

International Nuclear Information System (INIS)

Kopač, D.; Mundell, C. G.; Kobayashi, S.; Virgili, F. J.; Harrison, R.; Japelj, J.; Gomboc, A.; Guidorzi, C.; Melandri, A.

2015-01-01

We present predictions of centimeter and millimeter radio emission from reverse shocks (RSs) in the early afterglows of gamma-ray bursts (GRBs) 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 parameterization 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. and Melandri et al. in which the typical frequency of the RS was suggested to lie at radio rather than optical wavelengths at early times, we show that the brightest and most distinct RS 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 optical peaks, high isotropic energies, lower circumburst medium densities, and at observing frequencies that are less prone to synchrotron self-absorption effects—typically above a few GHz. Given recent detections of polarized prompt gamma-ray and optical RS emission, we suggest that detection of polarized radio/millimeter emission will unambiguously confirm the presence of low-frequency RSs at early time

VERITAS UPPER LIMIT ON THE VERY HIGH ENERGY EMISSION FROM THE RADIO GALAXY NGC 1275

International Nuclear Information System (INIS)

Acciari, V. A.; Benbow, W.; Aliu, E.; Boltuch, D.; Arlen, T.; Celik, O.; Aune, T.; Bautista, M.; Cogan, P.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R.; Bradbury, S. M.; Byrum, K.; Cannon, A.; Cesarini, A.; Ciupik, L.; Cui, W.; Duke, C.

2009-01-01

The recent detection by the Fermi γ-ray space telescope of high-energy γ-rays from the radio galaxy NGC 1275 makes the observation of the very high energy (VHE: E>100 GeV) part of its broadband spectrum particularly interesting, especially for the understanding of active galactic nuclei with misaligned multi-structured jets. The radio galaxy NGC 1275 was recently observed by VERITAS at energies above 100 GeV for about 8 hr. No VHE γ-ray emission was detected by VERITAS from NGC 1275. A 99% confidence level upper limit of 2.1% of the Crab Nebula flux level is obtained at the decorrelation energy of approximately 340 GeV, corresponding to 19% of the power-law extrapolation of the Fermi Large Area Telescope result.

A Multiwavelength Exploration of the Grand Design Spiral M83: Diffuse X-ray Emission

Science.gov (United States)

Kuntz, K. D.; Long, K. S.; Blair, W. P.; Plucinsky, P. P.; Soria, R.; Winkler, P. F.

2013-01-01

We have obtained a series of deep X-ray images of the nearby galaxy M83, with a total exposure 729 ksec with the Chandra ACIS-S array. Since the bulk of the X-ray emitting disk falls within the BI chip, these observations allow a detailed study of the soft diffuse emission in the disk. Most of the diffuse emission is related to star-formation regions and must be powered by supernovae and stellar winds, though the amount of emission due to identifiable SNR is only a few percent. The relation between the spectral shape and surface brightness that was seen in M101 suggests that the properties of the X-ray emission in spiral disks are shaped by the local hot gas production rate (traced by the local star-formation rate) or the disk mid-plane pressure, but it is unclear which physical mechanism dominates. To illuminate this problem, we will compare M83 with the previous Chandra studies of M101 and M33.

The Sun Radio Imaging Space Experiment (SunRISE) Mission

Science.gov (United States)

Kasper, J. C.; Lazio, J.; Alibay, F.; Amiri, N.; Bastian, T.; Cohen, C.; Landi, E.; Hegedus, A. M.; Maksimovic, M.; Manchester, W.; Reinard, A.; Schwadron, N.; Cecconi, B.; Hallinan, G.; Krupar, V.

2017-12-01

Radio emission from coronal mass ejections (CMEs) is a direct tracer of particle acceleration in the inner heliosphere and potential magnetic connections from the lower solar corona to the larger heliosphere. Energized electrons excite Langmuir waves, which then convert into intense radio emission at the local plasma frequency, with the most intense acceleration thought to occur within 20 R_S. The radio emission from CMEs is quite strong such that only a relatively small number of antennas is required to detect and map it, but many aspects of this particle acceleration and transport remain poorly constrained. Ground-based arrays would be quite capable of tracking the radio emission associated with CMEs, but absorption by the Earth's ionosphere limits the frequency coverage of ground-based arrays (nu > 15 MHz), which in turn limits the range of solar distances over which they can track the radio emission (concept: A constellation of small spacecraft in a geostationary graveyard orbit designed to localize and track radio emissions in the inner heliosphere. Each spacecraft would carry a receiving system for observations below 25 MHz, and SunRISE would produce the first images of CMEs more than a few solar radii from the Sun. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

THE 1.6 μm NEAR-INFRARED NUCLEI OF 3C RADIO GALAXIES: JETS, THERMAL EMISSION, OR SCATTERED LIGHT?

International Nuclear Information System (INIS)

Baldi, Ranieri D.; Chiaberge, Marco; Sparks, William; Macchetto, F. Duccio; Capetti, Alessandro; O'Dea, Christopher P.; Axon, David J.; Baum, Stefi A.; Quillen, Alice C.

2010-01-01

Using HST NICMOS 2 observations we have measured 1.6 μm near-infrared nuclear luminosities of 100 3CR radio galaxies with z < 0.3, by modeling and subtracting the extended emission from the host galaxy. We performed a multiwavelength statistical analysis (including optical and radio data) of the properties of the nuclei following classification of the objects into FR I and FR II, and low-ionization galaxies (LIGs), high-ionization galaxies (HIGs), and broad-line objects (BLOs) using the radio morphology and optical spectra, respectively. The correlations among near-infrared, optical, and radio nuclear luminosity support the idea that the near-infrared nuclear emission of FR Is has a non-thermal origin. Despite the difference in radio morphology, the multiwavelength properties of FR II LIG nuclei are statistically indistinguishable from those of FR Is, an indication of a common structure of the central engine. All BLOs show an unresolved near-infrared nucleus and a large near-infrared excess with respect to FR II LIGs and FR Is of equal radio core luminosity. This requires the presence of an additional (and dominant) component other than the non-thermal light. Considering the shape of their spectral energy distribution, we ascribe the origin of their near-infrared light to hot circumnuclear dust. A near-infrared excess is also found in HIGs, but their nuclei are substantially fainter than those of BLO. This result indicates that substantial obscuration along the line of sight to the nuclei is still present at 1.6 μm. Nonetheless, HIG nuclei cannot simply be explained in terms of dust obscuration: a significant contribution from light reflected in a circumnuclear scattering region is needed to account for their multiwavelength properties.

Radio continuum observations of NML Cygni

International Nuclear Information System (INIS)

Gregory, P.C.; Seaquist, E.R.

1976-01-01

An attempt to detect thermal radio emission from a compact circumstellar cloud about the infrared star NML Cyg has been carried out at three frequencies, 2.7, 8.1, and 10.5 GHz. Although positive results were obtained with single-dish observations at 10.5 GHz, the radio emission is not from a circumstellar cloud about NML Cyg. Instead it is postulated that the emission is from an H ii region with an angular extent of approx.2'. The red print of the Sky Survey shows a faint nebulosity of comparable angular size overlapping the star's position, lending support to this interpretation. The interferometer observations at 2.7 and 8.1 GHz provide an upper limit on the radio emission from any compact circumstellar cloud about NML Cyg of 2.8 mJy, which is well below the flux density expected for the absorbing cloud postulated by Davies et al. (1972)

Constraining the neutrino emission of gravitationally lensed Flat-Spectrum Radio Quasars with ANTARES data

Energy Technology Data Exchange (ETDEWEB)

Adrián-Martínez, S.; Ardid, M.; Bou-Cabo, M. [Institut d' Investigació per a la Gestió Integrada de les Zones Costaneres (IGIC), Universitat Politècnica de València, C/ Paranimf 1, Gandia, 46730 Spain (Spain); Albert, A. [GRPHE - Institut universitaire de technologie de Colmar, 34 rue du Grillenbreit BP 50568, Colmar, 68008 France (France); André, M. [Technical University of Catalonia, Laboratory of Applied Bioacoustics, Rambla Exposició, Vilanova i la Geltrú, Barcelona, 08800 Spain (Spain); Anton, G. [Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen Centre for Astroparticle Physics, Erwin-Rommel-Str. 1, Erlangen, 91058 Germany (Germany); Aubert, J.-J.; Bertin, V.; Brunner, J.; Busto, J. [Aix Marseille Université, CNRS/IN2P3, CPPM UMR 7346, Marseille, 13288 France (France); Baret, B. [APC, AstroParticule et Cosmologie, Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris, Sorbonne Paris Cité, 10, rue Alice Domon et Léonie Duquet, Paris Cedex 13, F-75205 France (France); Barrios-Martí, J. [IFIC - Instituto de Física Corpuscular, Edificios Investigación de Paterna, CSIC - Universitat de València, Apdo de Correos 22085, Valencia, 46071 Spain (Spain); Basa, S. [LAM - Laboratoire d' Astrophysique de Marseille, Pôle de l' Étoile Site de Château-Gombert, rue Frédéric Joliot-Curie 38, Marseille Cedex 13, 13388 France (France); Biagi, S. [INFN - Sezione di Bologna, Viale Berti-Pichat 6/2, Bologna, 40127 Italy (Italy); Bogazzi, C.; Bormuth, R.; Bouwhuis, M.C.; Bruijn, R. [Nikhef, Science Park 105, Amsterdam, 1098XG The Netherlands (Netherlands); Capone, A. [INFN -Sezione di Roma, P.le Aldo Moro 2, Roma, 00185 Italy (Italy); Caramete, L., E-mail: antares.spokesperson@in2p3.fr [Institute for Space Sciences, Bucharest, Măgurele, R-77125 Romania (Romania); and others

2014-11-01

This paper proposes to exploit gravitational lensing effects to improve the sensitivity of neutrino telescopes to the intrinsic neutrino emission of distant blazar populations. This strategy is illustrated with a search for cosmic neutrinos in the direction of four distant and gravitationally lensed Flat-Spectrum Radio Quasars. The magnification factor is estimated for each system assuming a singular isothermal profile for the lens. Based on data collected from 2007 to 2012 by the ANTARES neutrino telescope, the strongest constraint is obtained from the lensed quasar B0218+357, providing a limit on the total neutrino luminosity of this source of 1.08× 10{sup 46} erg s{sup -1}. This limit is about one order of magnitude lower than those previously obtained in the ANTARES standard point source searches with non-lensed Flat-Spectrum Radio Quasars.

Galactic radio astronomy

CERN Document Server

Sofue, Yoshiaki

2017-01-01

This book is a concise primer on galactic radio astronomy for undergraduate and graduate students, and provides wide coverage of galactic astronomy and astrophysics such as the physics of interstellar matter and the dynamics and structure of the Milky Way Galaxy and galaxies. Radio astronomy and its technological development have led to significant progress in galactic astronomy and contributed to understanding interstellar matter and galactic structures. The book begins with the fundamental physics of radio-wave radiation, i.e., black body radiation, thermal emission, synchrotron radiation, and HI and molecular line emissions. The author then gives overviews of ingredients of galactic physics, including interstellar matter such as the neutral (HI), molecular hydrogen, and ionized gases, as well as magnetic fields in galaxies. In addition, more advanced topics relevant to the Galaxy and galaxies are also contained here: star formation, supernova remnants, the Galactic Center and black holes, galactic dynamics...

Field emission from ZnS nanorods synthesized by radio frequency magnetron sputtering technique

Science.gov (United States)

Ghosh, P. K.; Maiti, U. N.; Jana, S.; Chattopadhyay, K. K.

2006-11-01

The field emission property of zinc sulphides nanorods synthesized in the thin film form on Si substrates has been studied. It is seen that ZnS nanorod thin films showed good field emission properties with a low-macroscopic turn-on field (2.9-6.3 V/μm). ZnS nanorods were synthesized by using radio frequency magnetron sputtering of a polycrystalline prefabricated ZnS target at a relatively higher pressure (10 -1 mbar) and at a lower substrate temperature (233-273 K) without using any catalyst. Transmission electron microscopic image showed the formation of ZnS nanorods with high aspect ratio (>60). The field emission data were analysed using Fowler-Nordhiem theory and the nearly straight-line nature of the F-N plots confirmed cold field emission of electrons. It was also found that the turn-on field decreased with the decrease of nanorod's diameters. The optical properties of the ZnS nanorods were also studied. From the measurements of transmittance of the films deposited on glass substrates, the direct allowed bandgap values have been calculated and they were in the range 3.83-4.03 eV. The thickness of the films was ˜600 nm.

VizieR Online Data Catalog: Galaxy clusters: radio halos, relics and parameters (Yuan+, 2015)

Science.gov (United States)

Yuan, Z. S.; Han, J. L.; Wen, Z. L.

2017-10-01

A large number of radio halos, relics, and mini-halos have been discovered and measured in recent decades through observations with VLA (e.g., Giovannini & Feretti 2000NewA....5..335G; van Weeren et al. 2011A&A...533A..35V), GMRT (e.g., Venturi et al. 2007A&A...463..937V; Kale et al. 2015A&A...579A..92K), WSRT (e.g., van Weeren et al. 2010Sci...330..347V; Trasatti et al. 2015A&A...575A..45T), and also ATCA (e.g., Shimwell et al. 2014MNRAS.440.2901S, 2015MNRAS.449.1486S). We have checked the radio images of radio halos, relics, and mini-halos in the literature and collected in Table 1 the radio flux Sν at frequencies within a few per cent around 1.4 GHz, 610 MHz, and 325 MHz; we have interpolated the flux at an intermediate frequency if measurements are available at higher and lower frequencies. To establish reliable scaling relations, we include only the very firm detection of diffuse radio emission in galaxy clusters, and omit questionable detections or flux estimates due to problematic point-source subtraction. (3 data files).

The radio continuum-star formation rate relation in WSRT sings galaxies

International Nuclear Information System (INIS)

Heesen, Volker; Brinks, Elias; Leroy, Adam K.; Heald, George; Braun, Robert; Bigiel, Frank; Beck, Rainer

2014-01-01

We present a study of the spatially resolved radio continuum-star formation rate (RC-SFR) relation using state-of-the-art star formation tracers in a sample of 17 THINGS galaxies. We use SFR surface density (Σ SFR ) maps created by a linear combination of GALEX far-UV (FUV) and Spitzer 24 μm maps. We use RC maps at λλ22 and 18 cm from the WSRT SINGS survey and Hα emission maps to correct for thermal RC emission. We compare azimuthally averaged radial profiles of the RC and FUV/mid-IR (MIR) based Σ SFR maps and study pixel-by-pixel correlations at fixed linear scales of 1.2 and 0.7 kpc. The ratio of the integrated SFRs from the RC emission to that of the FUV/MIR-based SF tracers is R int =0.78±0.38, consistent with the relation by Condon. We find a tight correlation between the radial profiles of the radio and FUV/MIR-based Σ SFR for the entire extent of the disk. The ratio R of the azimuthally averaged radio to FUV/MIR-based Σ SFR agrees with the integrated ratio and has only quasi-random fluctuations with galactocentric radius that are relatively small (25%). Pixel-by-pixel plots show a tight correlation in log-log diagrams of radio to FUV/MIR-based Σ SFR , with a typical standard deviation of a factor of two. Averaged over our sample we find (Σ SFR ) RC ∝(Σ SFR ) hyb 0.63±0.25 , implying that data points with high Σ SFR are relatively radio dim, whereas the reverse is true for low Σ SFR . We interpret this as a result of spectral aging of cosmic-ray electrons (CREs), which are diffusing away from the star formation sites where they are injected into the interstellar medium. This is supported by our finding that the radio spectral index is a second parameter in pixel-by-pixel plots: those data points dominated by young CREs are relatively radio dim, while those dominated by old CREs are slightly more RC bright than what would be expected from a linear extrapolation. We studied the ratio R of radio to FUV/MIR-based integrated SFR as a function of

Diffuse galactic continuum emission measured by COMPTEL and the cosmic-ray electron spectrum

Science.gov (United States)

Strong, A. W.; Diehl, R.; Schoenfelder, V.; Varendorff, M.; Youssefi, G.; Bloemen, H.; Hermsen, W.; De Vries, C.; Morris, D.; Stacy, J. G.

1994-01-01

Diffuse galactic continuum gamma-ray emission in the 0.75-30 MeV range from the inner Galaxy has been studied using data from COMPTEL on the Compton Gamma-Ray Observatory. Observations of the inner Galaxy from the Sky Survey have been used. The imaging properties of COMPTEL enable spatial analysis of the gamma-ray distribution using model fitting. A model based on atomic and molecular gas distributions in the Galaxy has been used to derive the emissivity spectrum of the gamma-ray emission and this spectrum is compared with theoretical estimates of bremsstrahlung emission from cosmic-ray electrons.

Millimeter observations of radio-loud active galaxies

NARCIS (Netherlands)

van Bemmel, IM; Bertoldi, F

In order to study the nature of the far-infrared emission observed in radio-loud active galaxies, we have obtained 1.2 mill observations with the IRAM 30 m telescope for a sample of eight radio-loud active galaxies. In all objects we find that the 1.2 mm emission is dominated by non-thermal

Pollutant emission and noise radiation from open and impinging inverse diffusion flames

International Nuclear Information System (INIS)

Choy, Y.S.; Zhen, H.S.; Leung, C.W.; Li, H.B.

2012-01-01

Highlights: ► The effect of burner geometry (d air and S) on inverse diffusion flames is studied. ► With fixed air/fuel supplies, a smaller d air curtails NO x emission but augments noise radiation. ► With fixed air/fuel supplies, a larger S reduces NO x emission but increases noise radiation. ► Both NO x emission and noise radiation are maximum under stoichiometric combustion. ► Impinging flames are nosier than corresponding open flames due to the mirror effect of the plate. -- Abstract: This paper reports an experimental investigation of the pollutant emission and noise radiation characteristics of both open and impinging inverse diffusion flames (IDFs), produced by five burners of different air port diameter (d air = 5, 6 and 6.84 mm) and air-to-fuel spacing (S = 8, 11.5 and 15 mm). The effects of d air , S, overall equivalence ratio φ and nozzle-to-plate spacing H on the pollutant emissions of CO and NO x and the noise radiation are examined. The results show that at fixed air flow rate, a smaller d air curtails NO x emission but augments noise radiation, indicative of a role played by turbulence, which tends to decrease pollutant emission and increase noise radiation. A larger S reduces NO x emission but increases noise radiation, indicating that different flame zones may be responsible for pollutant emission and noise radiation. When the IDF is under stoichiometric φ = 1.6, both the NO x emission and noise radiation are highest, as a result of maximum heat release rate. A comparison of EINO x for the open and impinging IDFs shows that the impinging IDFs emit more NO x probably due to the absence of NO reburning. The impinging IDFs have higher noise radiation than the corresponding open IDFs. A higher level of noise radiation from the impinging IDFs is observed as the target plate is brought closer to the burner.

RADIO VARIABILITY IN SEYFERT NUCLEI

International Nuclear Information System (INIS)

Mundell, C. G.; Ferruit, P.; Nagar, N.; Wilson, A. S.

2009-01-01

Comparison of 8.4 GHz radio images of a sample of eleven, early-type Seyfert galaxies with previous observations reveals possible variation in the nuclear radio flux density in five of them over a seven year period. Four Seyferts (NGC 2110, NGC 3081, MCG -6-30-15, and NGC 5273) show a decline in their 8.4 GHz nuclear flux density between 1992 and 1999, while one (NGC 4117) shows an increase; the flux densities of the remaining six Seyferts (Mrk 607, NGC 1386, Mrk 620, NGC 3516, NGC 4968, and NGC 7465) have remained constant over this period. New images of MCG -5-23-16 are also presented. We find no correlation between radio variability and nuclear radio luminosity or Seyfert nuclear type, although the sample is small and dominated by type 2 Seyferts. Instead, a possible correlation between the presence of nuclear radio variability and the absence of hundred parsec-scale radio emission is seen, with four out of five marginally resolved or unresolved nuclei showing a change in nuclear flux density, while five out of six extended sources show no nuclear variability despite having unresolved nuclear sources. NGC 2110 is the only source in our sample with significant extended radio structure and strong nuclear variability (∼38% decline in nuclear flux density over seven years). The observed nuclear flux variability indicates significant changes are likely to have occurred in the structure of the nucleus on scales smaller than the VLA beam size (i.e., within the central ∼0.''1 (15 pc)), between the two epochs, possibly due to the appearance and fading of new components or shocks in the jet, consistent with previous detection of subparsec-scale nuclear structure in this Seyfert. Our results suggest that all Seyferts may exhibit variation in their nuclear radio flux density at 8.4 GHz, but that variability is more easily recognized in compact sources in which emission from the variable nucleus is not diluted by unresolved, constant flux density radio jet emission

The Analysis of the Possible Thermal Emission at Radio Frequencies from an Evolved Supernova Remnant HB 3 (G132.7+1.3: Revisited

Directory of Open Access Journals (Sweden)

Onić, D.

2008-12-01

Full Text Available It has recently been reported that some of the flux density values for an evolved supernova remnant (SNR HB 3 (G132.7$+$1.3 are not accurate enough. In this work we therefore revised the analysis of the possible thermal emission at radio frequencies from this SNR using the recently published, corrected flux density values. A model including the sum of non-thermal (purely synchrotron and thermal (bremsstrahlung components is applied to fit the integrated radio spectrum of this SNR. The contribution of thermal component to the total volume emissivity at $1 mathrm{GHz}$ is estimated to be $approx37 \\%$. The ambient density is also estimated to be $napprox 9 mathrm{cm}^{-3}$ for $mathrm{T}=10^{4} mathrm{K}$. Again we obtained a relatively significant presence of thermal emission at radio frequencies from the SNR, which can support interaction between SNR HB 3 and adjacent molecular cloud associated with the mbox{H,{sc ii}} region W3. Our model estimates for thermal component contribution to total volume emissivity at $1 mathrm{GHz}$ and ambient density are similar to those obtained earlier ($approx40 \\%$, $approx10 mathrm{cm^{-3}}$. It is thus obvious that the corrected flux density values do not affect the basic conclusions.

Radio continuum, far infrared and star formation

International Nuclear Information System (INIS)

Wielebinski, R.; Wunderlich, E.; Klein, U.; Hummel, E.

1987-01-01

A very tight correlation was found between the radio emission and the far infrared emission from galaxies. This has been found for various samples of galaxies and is explained in terms of recent star formation. The tight correlation would imply that the total radio emission is a good tracer of star formation. The correlation between the radio power at 5 GHz and the far infrared luminosity is shown. The galaxies are of various morphological types and were selected from the various IRAS circulars, hence the sample is an infrared selected sample. The far infrared luminosities were corrected for the dust temperature. This is significant because it decreases the dispersion in the correlation

Modelling blazar flaring using a time-dependent fluid jet emission model - an explanation for orphan flares and radio lags

Science.gov (United States)

Potter, William J.

2018-01-01

Blazar jets are renowned for their rapid violent variability and multiwavelength flares, however, the physical processes responsible for these flares are not well understood. In this paper, we develop a time-dependent inhomogeneous fluid jet emission model for blazars. We model optically thick radio flares for the first time and show that they are delayed with respect to the prompt optically thin emission by ∼months to decades, with a lag that increases with the jet power and observed wavelength. This lag is caused by a combination of the travel time of the flaring plasma to the optically thin radio emitting sections of the jet and the slow rise time of the radio flare. We predict two types of flares: symmetric flares - with the same rise and decay time, which occur for flares whose duration is shorter than both the radiative lifetime and the geometric path-length delay time-scale; extended flares - whose luminosity tracks the power of particle acceleration in the flare, which occur for flares with a duration longer than both the radiative lifetime and geometric delay. Our model naturally produces orphan X-ray and γ-ray flares. These are caused by flares that are only observable above the quiescent jet emission in a narrow band of frequencies. Our model is able to successfully fit to the observed multiwavelength flaring spectra and light curves of PKS1502+106 across all wavelengths, using a transient flaring front located within the broad-line region.

Radio and γ -Ray Variability in the BL Lac PKS 0219−164: Detection of Quasi-periodic Oscillations in the Radio Light Curve

Energy Technology Data Exchange (ETDEWEB)

Bhatta, Gopal, E-mail: gopalbhatta716@gmail.com [Astronomical Observatory of the Jagiellonian University, ul. Orla 171, 30-244 Kraków (Poland); Mt. Suhora Observatory, Pedagogical University, ul. Podchorazych 2, 30-084 Kraków (Poland)

2017-09-20

In this work, we explore the long-term variability properties of the blazar PKS 0219−164 in the radio and the γ -ray regime, utilizing the OVRO 15 GHz and the Fermi /LAT observations from the period 2008–2017. We found that γ -ray emission is more variable than the radio emission implying that γ -ray emission possibly originated in more compact regions while the radio emission represented continuum emission from the large-scale jets. Also, in the γ -ray, the source exhibited spectral variability, characterized by the softer-when-brighter trend, a less frequently observed feature in the high-energy emission by BL Lacs. In radio, using Lomb–Scargle periodogram and weighted wavelet z -transform, we detected a strong signal of quasi-periodic oscillation (QPO) with a periodicity of 270 ± 26 days with possible harmonics of 550 ± 42 and 1150 ± 157 day periods. At a time when detections of QPOs in blazars are still under debate, the observed QPO with high statistical significance (∼97%–99% global significance over underlying red-noise processes) and persistent over nearly 10 oscillations could make one of the strongest cases for the detection of QPOs in blazar light curves. We discuss various blazar models that might lead to the γ -ray and radio variability, QPO, and the achromatic behavior seen in the high-energy emission from the source.

STAR FORMATION SUPPRESSION DUE TO JET FEEDBACK IN RADIO GALAXIES WITH SHOCKED WARM MOLECULAR GAS

International Nuclear Information System (INIS)

Lanz, Lauranne; Ogle, Patrick M.; Appleton, Philip N.; Alatalo, Katherine

2016-01-01

We present Herschel observations of 22 radio galaxies, selected for the presence of shocked, warm molecular hydrogen emission. We measured and modeled spectral energy distributions in 33 bands from the ultraviolet to the far-infrared to investigate the impact of jet feedback on star formation activity. These galaxies are massive, early-type galaxies with normal gas-to-dust ratios, covering a range of optical and infrared colors. We find that the star formation rate (SFR) is suppressed by a factor of ∼3–6, depending on how molecular gas mass is estimated. We suggest that this suppression is due to the shocks driven by the radio jets injecting turbulence into the interstellar medium (ISM), which also powers the luminous warm H 2 line emission. Approximately 25% of the sample shows suppression by more than a factor of 10. However, the degree of SFR suppression does not correlate with indicators of jet feedback including jet power, diffuse X-ray emission, or intensity of warm molecular H 2 emission, suggesting that while injected turbulence likely impacts star formation, the process is not purely parameterized by the amount of mechanical energy dissipated into the ISM. Radio galaxies with shocked warm molecular gas cover a wide range in SFR–stellar mass space, indicating that these galaxies are in a variety of evolutionary states, from actively star-forming and gas-rich to quiescent and gas-poor. SFR suppression appears to have the largest impact on the evolution of galaxies that are moderately gas-rich.

Discovery of megaparsec-scale, low surface brightness nonthermal emission in merging galaxy clusters using the green bank telescope

Energy Technology Data Exchange (ETDEWEB)

Farnsworth, Damon; Rudnick, Lawrence [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church Street S.E., Minneapolis, MN 55455 (United States); Brown, Shea [Department of Physics and Astronomy, University of Iowa, 203 Van Allen Hall, Iowa City, IA 52242 (United States); Brunetti, Gianfranco [INAF/Istituto di Radioastronomia, via Gobetti 101, I-40129 Bologna (Italy)

2013-12-20

We present results from a study of 12 X-ray bright clusters at 1.4 GHz with the 100 m Green Bank Telescope. After subtraction of point sources using existing interferometer data, we reach a median (best) 1σ rms sensitivity level of 0.01 (0.006) μJy arcsec{sup –2}, and find a significant excess of diffuse, low surface brightness emission in 11 of 12 Abell clusters observed. We also present initial results at 1.4 GHz of A2319 from the Very Large Array. In particular, we find: (1) four new detections of diffuse structures tentatively classified as two halos (A2065, A2069) and two relics (A2067, A2073); (2) the first detection of the radio halo in A2061 at 1.4 GHz, which qualifies this as a possible ultra-steep spectrum halo source with a synchrotron spectral index of α ∼ 1.8 between 327 MHz and 1.4 GHz; (3) a ∼2 Mpc radio halo in the sloshing, minor-merger cluster A2142; (4) a >2× increase of the giant radio halo extent and luminosity in the merging cluster A2319; (5) a ∼7× increase to the integrated radio flux and >4× increase to the observed extent of the peripheral radio relic in A1367 to ∼600 kpc, which we also observe to be polarized on a similar scale; (6) significant excess emission of ambiguous nature in three clusters with embedded tailed radio galaxies (A119, A400, A3744). Our radio halo detections agree with the well-known X-ray/radio luminosity correlation, but they are larger and fainter than current radio power correlation studies would predict. The corresponding volume-averaged synchrotron emissivities are 1-2 orders of magnitude below the characteristic value found in previous studies. Some of the halo-like detections may be some type of previously unseen, low surface brightness radio halo or blend of unresolved shock structures and sub-Mpc-scale turbulent regions associated with their respective cluster merging activity. Four of the five tentative halos contain one or more X-ray cold fronts, suggesting a possible connection between gas

Portable Wireless Device Threat Assessment for Aircraft Navigation Radios

Science.gov (United States)

Nguyen, Truong X.; Koppen, Sandra V.; Ely, Jay J.; Williams, Reuben A.; Smith, Laura J.; Salud, Maria Theresa P.

2004-01-01

This paper addresses the concern for Wireless Local Area Network devices and two-way radios to cause electromagnetic interference to aircraft navigation radio systems. Spurious radiated emissions from various IEEE 802.11a, 802.11b, and Bluetooth devices are characterized using reverberation chambers. The results are compared with baseline emissions from standard laptop computer and personal digital assistants (PDAs) that are currently allowed for use on aircraft. The results indicate that the WLAN devices tested are not more of a threat to aircraft navigation radios than standard laptop computers and PDAs in most aircraft bands. In addition, spurious radiated emission data from seven pairs of two-way radios are provided. These two-way radios emit at much higher levels in the bands considered. A description of the measurement process, device modes of operation and the measurement results are reported.

TURBULENT COSMIC-RAY REACCELERATION AT RADIO RELICS AND HALOS IN CLUSTERS OF GALAXIES

International Nuclear Information System (INIS)

Fujita, Yutaka; Takizawa, Motokazu; Yamazaki, Ryo; Akamatsu, Hiroki; Ohno, Hiroshi

2015-01-01

Radio relics are synchrotron emission found on the periphery of galaxy clusters. From the position and the morphology, it is often believed that the relics are generated by cosmic-ray (CR) electrons accelerated at shocks through a diffusive shock acceleration (DSA) mechanism. However, some radio relics have harder spectra than the prediction of the standard DSA model. One example is observed in the cluster 1RXS J0603.3+4214, which is often called the “Toothbrush Cluster.” Interestingly, the position of the relic is shifted from that of a possible shock. In this study, we show that these discrepancies in the spectrum and the position can be solved if turbulent (re)acceleration is very effective behind the shock. This means that for some relics turbulent reacceleration may be the main mechanism to produce high-energy electrons, contrary to the common belief that it is the DSA. Moreover, we show that for efficient reacceleration, the effective mean free path of the electrons has to be much smaller than their Coulomb mean free path. We also study the merging cluster 1E 0657−56, or the “Bullet Cluster,” in which a radio relic has not been found at the position of the prominent shock ahead of the bullet. We indicate that a possible relic at the shock is obscured by the observed large radio halo that is generated by strong turbulence behind the shock. We propose a simple explanation of the morphological differences of radio emission among the Toothbrush, the Bullet, and the Sausage (CIZA J2242.8+5301) Clusters

PROBING SHOCK BREAKOUT AND PROGENITORS OF STRIPPED-ENVELOPE SUPERNOVAE THROUGH THEIR EARLY RADIO EMISSIONS

Energy Technology Data Exchange (ETDEWEB)

Maeda, Keiichi, E-mail: keiichi.maeda@ipmu.jp [Kavli Institute for the Physics and Mathematics of the Universe (Kavli-IPMU), Todai Institutes for Advanced Study (TODIAS), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan)

2013-01-01

We study properties of early radio emission from stripped-envelope supernovae (SNe; those of Type IIb/Ib/Ic). We suggest there is a sub-class of stripped-envelope SNe based on their radio properties, including the optically well-studied Type Ic SNe (SNe Ic) 2002ap and 2007gr, showing a rapid rise to a radio peak within {approx}10 days and reaching a low luminosity (at least an order of magnitude fainter than a majority of SNe IIb/Ib/Ic). They show a decline after the peak that is shallower than that of other stripped-envelope SNe while their spectral index is similar. We show that all these properties are naturally explained if the circumstellar material (CSM) density is low and therefore the forward shock is expanding into the CSM without deceleration. Since the forward shock velocity in this situation, as estimated from the radio properties, still records the maximum velocity of the SN ejecta following the shock breakout, observing these SNe in radio wavelengths provides new diagnostics on the nature of both the breakout and the progenitor which otherwise require a quite rapid follow-up in other wavelengths. The inferred post-shock breakout velocities of SNe Ic 2002ap and 2007gr are sub-relativistic, {approx}0.3c. These are higher than that inferred for SN II 1987A, in line with suggested compact progenitors. However, these are lower than expected for a Wolf-Rayet (W-R) progenitor. It may reflect an as yet unresolved nature of the progenitors just before the explosion, and we suggest that the W-R progenitor envelopes might have been inflated which could quickly reduce the maximum ejecta velocity from the initial shock breakout velocity.

Radio emission from quasars and BL Lac objects by coherent plasma oscillation and stimulated Compton scattering

International Nuclear Information System (INIS)

Colgate, S.A.; Petschek, A.G.

1978-01-01

The full radiation spectrum of quasars and BL Lac objects is interpreted as due to a dependent combination of a soft plasma oscillation source at 2ν/sub P/ and bremsstrahlung. Previous work of the plasma oscillation radiation is extended into the radio part of the spectrum and it is shown how the high brightness temperature observations of BL Lac objects [kT/sub b/ (100 MHz) approximate = 3 x 10 5 mc 2 ] are a reasonable consequence of a lower external plasma density and ejection as required for the observed lack of emission lines. Two extreme cases are considered, the one where the plasma oscillations are suddenly extinguished and only stimulated Compton scattering remains and a second case of a constant source of plasma oscillations but a graded surface density. The first case gives 1/100 of the required brightness temperature and the second gives 100 times too large a brightness temperature and also a x 10 too large a radius. It is believed reasonable to invoke a combination of both processes to explain the observed radio spectrum. This model circumvents the self-Compton x-ray flux difficulty of incoherent synchrotron emission

CORRELATIONS OF QUASAR OPTICAL SPECTRA WITH RADIO MORPHOLOGY

International Nuclear Information System (INIS)

Kimball, Amy E.; Ivezic, Zeljko; Wiita, Paul J.; Schneider, Donald P.

2011-01-01

Using the largest homogeneous quasar sample with high-quality optical spectra and robust radio morphology classifications assembled to date, we investigate relationships between radio and optical properties with unprecedented statistical power. The sample consists of 4714 radio quasars from FIRST with S 20 ≥ 2 mJy and with spectra from the Sloan Digital Sky Survey (SDSS). Radio morphology classes include core-only (core), core-lobe (lobe), core-jet (jet), lobe-core-lobe (triple), and double-lobe. Electronic tables of the quasar samples, along with spectral composites for individual morphology classes, are made available. We examine the optical colors of these subsamples and find that radio quasars with core emission unresolved by FIRST (on ∼5'' scale) have a redder color distribution than radio-quiet quasars (S 20 ∼ I ) are correlated, which supports the hypothesis that both parameters are indicative of line-of-sight orientation. We investigate spectral line equivalent widths (EWs) as a function of R and R I , including the O [III] narrow line doublet and the C IV λ1549 and Mg II λ2799 broad lines. We find that the rest EWs of the broad lines correlate positively with R I at the 4σ-8σ level. However, we find no strong dependence of EW on R, in contrast to previously published results. A possible interpretation of these results is that EWs of quasar emission lines increase as the line-of-sight angle to the radio-jet axis decreases. These results are in stark contrast to commonly accepted orientation-based theories, which suggest that continuum emission should increase as the angle to the radio-jet axis decreases, resulting in smaller EWs of emission lines (assumed isotropic). Finally, we observe the Baldwin effect in our sample and find that it does not depend strongly on quasar radio morphology.

The collective radio properties of symbiotic stars

International Nuclear Information System (INIS)

Seaquist, E.R.; Taylor, A.R.

1990-01-01

Radio measurements of symbiotic stars are reported which extend the search for radio emission and provide multifrequency and multiepoch measurements of previously detected stars. The results show no evidence that there are time variations in excess of about 30 percent over a period of several years in the detected stars. The radio flux densities are correlated with brightness in the IR, especially at the longer IR wavelengths where dust emission dominates. It is confirmed that symbiotics with the latest red giant spectral types are the most luminous radio emitters. The D-types are the most radio-luminous. Virtually all detected stars with measurements at more than one frequency exhibit a positive spectral index, consistent with optically thick thermal bremsstrahlung. The binary separation for a number of radio-emitting symbiotics is estimated, and it is found that the distribution of inferred binary separations is dramatically different for IR D-types than for S-types. 37 refs

The magnetoionic modes and propagation properties of auroral radio emissions

International Nuclear Information System (INIS)

Calvert, W.; Hashimoto, Kozo

1990-01-01

The different magnetoionic wave modes which accompany the aurora are identified using DE 1 not only by their appearance on satellite radio spectrograms, but also by concurrent measurements of their wave polarization and arrival directions, and by ray-tracing models of their expected propagation behavior. Of the four possible propagation modes, designated O, X, W, and Z for the ordinary, extraordinary, whistler, and Z modes, respectively, all four are found to occur in the auroral zone, as follows: The most intense, of course, is the well-known auroral kilometric radiation (AKR), which originates primarily in the X mode near the electron cyclotron frequency, but which is frequently also accompanied by a weaker O-mode component from the same location. The next most prominent auroral emission is the W-mode auroral hiss originating from altitudes always well below the DE 1 satellite at frequencies below the local cyclotron frequency. The previously reported Z-mode auroral radiation was also detected, but from sources also below the satellite and at the poleward edge of the cavity, and not from the expected AKR source at the cyclotron frequency. A weaker O-mode component seems to accompany these emissions also, both within the polar cap poleward of the source and inside the cavity, the latter seemingly being guided upward by the cavity's lower plasma densities. Finally, exactly on the source field lines at the poleward edge of the cavity, there also occasionally seems to be localized Z-mode emissions extending from the Z-mode cutoff at quite low frequencies up to and above the plasma frequency

Long-term radio and X-ray evolution of the tidal disruption event ASASSN-14li

Science.gov (United States)

Bright, J. S.; Fender, R. P.; Motta, S. E.; Mooley, K.; Perrott, Y. C.; van Velzen, S.; Carey, S.; Hickish, J.; Razavi-Ghods, N.; Titterington, D.; Scott, P.; Grainge, K.; Scaife, A.; Cantwell, T.; Rumsey, C.

2018-04-01

We report on late time radio and X-ray observations of the tidal disruption event candidate ASASSN-14li, covering the first 1000 d of the decay phase. For the first ˜200 d the radio and X-ray emission fade in concert. This phase is better fitted by an exponential decay at X-ray wavelengths, while the radio emission is well described by either an exponential or the canonical t-5/3 decay assumed for tidal disruption events. The correlation between radio and X-ray emission during this period can be fitted as L_R∝ L_X^{1.9± 0.2}. After 400 d the radio emission at 15.5 GHz has reached a plateau level of 244 ± 8 μJy which it maintains for at least the next 600 d, while the X-ray emission continues to fade exponentially. This steady level of radio emission is likely due to relic radio lobes from the weak AGN-like activity implied by historical radio observations. We note that while most existing models are based upon the evolution of ejecta which are decoupled from the central black hole, the radio-X-ray correlation during the declining phase is also consistent with core-jet emission coupled to a radiatively efficient accretion flow.

First limits on the very-high energy gamma-ray afterglow emission of a fast radio burst. H.E.S.S. observations of FRB 150418

Science.gov (United States)

H.E.S.S. Collaboration; Abdalla, H.; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Andersson, T.; Angüner, E. O.; Arakawa, M.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Büchele, M.; Bulik, T.; Capasso, M.; Carr, J.; Casanova, S.; Cerruti, M.; Chakraborty, N.; Chalme-Calvet, R.; Chaves, R. C. G.; Chen, A.; Chevalier, J.; Chrétien, M.; Coffaro, M.; Colafrancesco, S.; Cologna, G.; Condon, B.; Conrad, J.; Cui, Y.; Davids, I. D.; Decock, J.; Degrange, B.; Deil, C.; Devin, J.; Dewilt, P.; Dirson, L.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O.'c.; Dutson, K.; Dyks, J.; Edwards, T.; Egberts, K.; Eger, P.; Ernenwein, J.-P.; Eschbach, S.; Farnier, C.; Fegan, S.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Funk, S.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Goyal, A.; Grondin, M.-H.; Hahn, J.; Haupt, M.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holler, M.; Horns, D.; Ivascenko, A.; Iwasaki, H.; Jacholkowska, A.; Jamrozy, M.; Janiak, M.; Jankowsky, D.; Jankowsky, F.; Jingo, M.; Jogler, T.; Jouvin, L.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katsuragawa, M.; Katz, U.; Kerszberg, D.; Khangulyan, D.; Khélifi, B.; Kieffer, M.; King, J.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Kraus, M.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lees, J.-P.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Leser, E.; Lohse, T.; Lorentz, M.; Liu, R.; López-Coto, R.; Lypova, I.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Morå, K.; Moulin, E.; Murach, T.; Nakashima, S.; de Naurois, M.; Niederwanger, F.; Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Öttl, S.; Ohm, S.; Ostrowski, M.; Oya, I.; Padovani, M.; Panter, M.; Parsons, R. D.; Pekeur, N. W.; Pelletier, G.; Perennes, C.; Petrucci, P.-O.; Peyaud, B.; Piel, Q.; Pita, S.; Poon, H.; Prokhorov, D.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Reimer, A.; Reimer, O.; Renaud, M.; de Los Reyes, R.; Richter, S.; Rieger, F.; Romoli, C.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Saito, S.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwemmer, S.; Seglar-Arroyo, M.; Settimo, M.; Seyffert, A. S.; Shafi, N.; Shilon, I.; Simoni, R.; Sol, H.; Spanier, F.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stycz, K.; Sushch, I.; Takahashi, T.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tibaldo, L.; Tiziani, D.; Tluczykont, M.; Trichard, C.; Tsuji, N.; Tuffs, R.; Uchiyama, Y.; van der Walt, D. J.; van Eldik, C.; van Rensburg, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zaborov, D.; Zacharias, M.; Zanin, R.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Żywucka, N.; Superb Collaboration; Jankowski, F.; Keane, E. F.; Petroff, E.

2017-01-01

Aims: Following the detection of the fast radio burst FRB150418 by the SUPERB project at the Parkes radio telescope, we aim to search for very-high energy gamma-ray afterglow emission. Methods: Follow-up observations in the very-high energy gamma-ray domain were obtained with the H.E.S.S. imaging atmospheric Cherenkov telescope system within 14.5 h of the radio burst. Results: The obtained 1.4 h of gamma-ray observations are presented and discussed. At the 99% C.L. we obtained an integral upper limit on the gamma-ray flux of Φγ(E > 350 GeV) FRB 150418. Conclusions: No hints for high-energy afterglow emission of FRB 150418 were found. Taking absorption on the extragalactic background light into account and assuming a distance of z = 0.492 based on radio and optical counterpart studies and consistent with the FRB dispersion, we constrain the gamma-ray luminosity at 1 TeV to L < 5.1 × 1047 erg/s at 99% C.L.

A Deep Chandra ACIS Study of NGC 4151. II. The Innermost Emission Line Region and Strong Evidence for Radio Jet-NLR Cloud Collision

Science.gov (United States)

Wang, Junfeng; Fabbiano, Giuseppina; Elvis, Martin; Risaliti, Guido; Mundell, Carole G.; Karovska, Margarita; Zezas, Andreas

2011-07-01

We have studied the X-ray emission within the inner ~150 pc radius of NGC 4151 by constructing high spatial resolution emission line images of blended O VII, O VIII, and Ne IX. These maps show extended structures that are spatially correlated with the radio outflow and optical [O III] emission. We find strong evidence for jet-gas cloud interaction, including morphological correspondences with regions of X-ray enhancement, peaks of near-infrared [Fe II] emission, and optical clouds. In these regions, moreover, we find evidence of elevated Ne IX/O VII ratios; the X-ray emission of these regions also exceeds that expected from nuclear photoionization. Spectral fitting reveals the presence of a collisionally ionized component. The thermal energy of the hot gas suggests that >~ 0.1% of the estimated jet power is deposited into the host interstellar medium through interaction between the radio jet and the dense medium of the circumnuclear region. We find possible pressure equilibrium between the collisionally ionized hot gas and the photoionized line-emitting cool clouds. We also obtain constraints on the extended iron and silicon fluorescent emission. Both lines are spatially unresolved. The upper limit on the contribution of an extended emission region to the Fe Kα emission is <~ 5% of the total, in disagreement with a previous claim that 65% of the Fe Kα emission originates in the extended narrow line region.

The importance of Radio Quiet Zone (RQZ) for radio astronomy

Science.gov (United States)

Umar, Roslan; Abidin, Zamri Zainal; Ibrahim, Zainol Abidin

2013-05-01

Most of radio observatories are located in isolated areas. Since radio sources from the universe is very weak, astronomer need to avoid radio frequency interference (RFI) from active spectrum users and radio noise produced by human made (telecommunication, mobile phone, microwave user and many more. There are many observatories around the world are surrounded by a Radio Quiet Zone (RQZ), which is it was set up using public or state laws. A Radio Quiet Zone normally consists of two areas: an exclusive area in which totally radio emissions are forbidden, with restrictions for residents and business developments, and a larger (radius up to 100 km above) coordination area where the power of radio transmission limits to threshold levels. Geographical Information System (GIS) can be used as a powerful tool in mapping large areas with varying RQZ profiles. In this paper, we report the initial testing of the usage of this system in order to identify the areas were suitable for Radio Quiet Zone. Among the important parameters used to develop the database for our GIS are population density, information on TV and telecommunication (mobile phones) transmitters, road networks (highway), and contour shielding. We will also use other information gathered from on-site RFI level measurements on selected 'best' areas generated by the GIS. The intention is to find the best site for the purpose of establishing first radio quiet zones for radio telescope in Malaysia.

Population Studies of Radio and Gamma-Ray Pulsars

Science.gov (United States)

Harding, Alice K; Gonthier, Peter; Coltisor, Stefan

2004-01-01

Rotation-powered pulsars are one of the most promising candidates for at least some of the 40-50 EGRET unidentified gamma-ray sources that lie near the Galactic plane. Since the end of the EGRO mission, the more sensitive Parkes Multibeam radio survey has detected mere than two dozen new radio pulsars in or near unidentified EGRET sources, many of which are young and energetic. These results raise an important question about the nature of radio quiescence in gamma-ray pulsars: is the non-detection of radio emission a matter of beaming or of sensitivity? The answer is very dependent on the geometry of the radio and gamma-ray beams. We present results of a population synthesis of pulsars in the Galaxy, including for the first time the full geometry of the radio and gamma-ray beams. We use a recent empirically derived model of the radio emission and luminosity, and a gamma-ray emission geometry and luminosity derived theoretically from pair cascades in the polar slot gap. The simulation includes characteristics of eight radio surveys of the Princeton catalog plus the Parkes MB survey. Our results indicate that EGRET was capable of detecting several dozen pulsars as point sources, with the ratio of radio-loud to radio-quiet gamma-ray pulsars increasing significantly to about ten to one when the Parkes Survey is included. Polar cap models thus predict that many of the unidentified EGRET sources could be radio-loud gamma- ray pulsars, previously undetected as radio pulsars due to distance, large dispersion and lack of sensitivity. If true, this would make gamma-ray telescopes a potentially more sensitive tool for detecting distant young neutron stars in the Galactic plane.

IA-Regional-Radio - Social Network for Radio Recommendation

Science.gov (United States)

Dziczkowski, Grzegorz; Bougueroua, Lamine; Wegrzyn-Wolska, Katarzyna

This chapter describes the functions of a system proposed for the music hit recommendation from social network data base. This system carries out the automatic collection, evaluation and rating of music reviewers and the possibility for listeners to rate musical hits and recommendations deduced from auditor's profiles in the form of regional Internet radio. First, the system searches and retrieves probable music reviews from the Internet. Subsequently, the system carries out an evaluation and rating of those reviews. From this list of music hits, the system directly allows notation from our application. Finally, the system automatically creates the record list diffused each day depending on the region, the year season, the day hours and the age of listeners. Our system uses linguistics and statistic methods for classifying music opinions and data mining techniques for recommendation part needed for recorded list creation. The principal task is the creation of popular intelligent radio adaptive on auditor's age and region - IA-Regional-Radio.

DISCOVERY OF γ -RAY EMISSION FROM THE RADIO-INTERMEDIATE QUASAR III ZW 2: VIOLENT JET ACTIVITY WITH INTRADAY γ -RAY VARIABILITY

Energy Technology Data Exchange (ETDEWEB)

Liao, Neng-Hui; Xin, Yu-Liang; Fan, Yi-Zhong [Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Fan, Xu-Liang [Graduate University of Chinese Academy of Sciences, Yuquan Road 19, Beijing 100049 (China); Weng, Shan-Shan [Department of Physics, Nanjing Normal University, Nanjing 210046 (China); Li, Shao-Kun [Key Laboratory for the Structure and Evolution of Celestial Objects, Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Chen, Liang, E-mail: liaonh@pmo.ac.cn, E-mail: yzfan@pmo.ac.cn [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)

2016-10-01

III Zw 2 is the prototype of radio-intermediate quasars. Although there is the evidence of possessing strong jet, significant γ -ray emission has not been reported before. In this work, we carry out a detailed analysis of the latest Fermi -LAT Pass  8 data. No significant γ -ray signal has been detected in the time-averaged 7-year Fermi -LAT data of III Zw 2; however, we have identified two distinct γ -ray flares with isotropic luminosities of ∼10{sup 45} erg s{sup −1}. Multiwavelength data analysis (also including the optical photometric observations from Yunnan Observatories) are presented and the main finding is simultaneous optical and γ -ray flares of III Zw 2 appearing in 2009 November. Violent γ -ray variability with a doubling timescale of 2.5 hr was detected in another γ -ray flare in May 2010, for which the 3-hr γ -ray peak flux is ∼250 times of the average flux in 7 years. Rather similar behaviors are observed in blazars and the blazar model can reasonably reproduce the spectral energy distribution of III Zw 2 in a wide energy range, strongly suggesting that its central engine resembles that of blazars. In view of its core, which shares radio similarities with young radio sources, together with weak extended radio lobe emission, we suggest that III Zw 2 harbors a recurrent activity core and thus serves as a valuable target for investigating the fueling and triggering of the activity in radio-loud active galactic nuclei.

Optical spectra and radio properties of quasars

International Nuclear Information System (INIS)

Wills, B.J.

1982-01-01

Using high quality spectrophotometric scans obtained at the McDonald Observatory, and data from the literature the author shows that, for quasars, the relative strength of optical Fe II emission (the broad blended feature lambda4570) may be roughly inversely proportional to line widths (full width at half maximum, FWHM). A similar relation between the relative intensity of the UV Fe II blend between 2300 and 2600 A (the lambda2500 feature) and the widths of Mg II and Hβ is shown. She distinguishes between compact and extended radio sources and includes radio quiet quasars, Seyfert 1 galaxies and BLRG's. The quasars associated with extended radio sources have the broadest emission lines and the weakest Fe II, falling close to the region occupied by BLRG's which also have extended radio structure. Those quasars with strong Fe II and compact radio structure are most similar to the Seyfert 1 galaxies. (Auth.)

Radio imaging of core-dominated high redshift quasars

DEFF Research Database (Denmark)

Barthel, Peter D.; Vestergaard, Marianne; Lonsdale, Colin J.

1999-01-01

VLA imaging at kiloparsec-scale resolution of sixteen core-dominated radio-loud QSOs is presented. Many objects appear to display variable radio emission and their radio morphologies are significantly smaller than those of steep-spectrum quasars, consistent with these objects being observed...

HOW ELSE CAN WE DETECT FAST RADIO BURSTS?

Energy Technology Data Exchange (ETDEWEB)

Lyutikov, Maxim [Department of Physics and Astronomy, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907-2036 (United States); Lorimer, Duncan R., E-mail: lyutikov@purdue.edu [Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506-6315 (United States)

2016-06-20

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{sup −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.

HOW ELSE CAN WE DETECT FAST RADIO BURSTS?

International Nuclear Information System (INIS)

Lyutikov, Maxim; Lorimer, Duncan R.

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. 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.

Normal and anomalous diffusion in fluctuations of dust concentration nearby emission source

Science.gov (United States)

Szczurek, Andrzej; Maciejewska, Monika; Wyłomańska, Agnieszka; Sikora, Grzegorz; Balcerek, Michał; Teuerle, Marek

2018-02-01

Particulate matter (PM) is an important component of air. Nowadays, major attention is payed to fine dust. It has considerable environmental impact, including adverse effect on human health. One of important issues regarding PM is the temporal variation of its concentration. The variation contains information about factors influencing this quantity in time. The work focuses on the character of PM concentration dynamics indoors, in the vicinity of emission source. The objective was to recognize between the homogeneous or heterogeneous dynamics. The goal was achieved by detecting normal and anomalous diffusion in fluctuations of PM concentration. For this purpose we used anomalous diffusion exponent, β which was derived from Mean Square Displacement (MSD) analysis. The information about PM concentration dynamics may be used to design sampling strategy, which serves to attain representative information about PM behavior in time. The data analyzed in this work was collected from single-point PM concentration monitoring in the vicinity of seven emission sources in industrial environment. In majority of cases we observed heterogeneous character of PM concentration dynamics. It confirms the complexity of interactions between the emission sources and indoor environment. This result also votes against simplistic approach to PM concentration measurement indoors, namely their occasional character, short measurement periods and long term averaging.

Radio transients from newborn black holes

Science.gov (United States)

Kashiyama, Kazumi; Hotokezaka, Kenta; Murase, Kohta

2018-05-01

We consider radio emission from a newborn black hole (BH), which is accompanied by a mini-disk with a mass of ≲ M⊙. Such a disk can be formed from an outer edge of the progenitor's envelope, especially for metal-poor massive stars and/or massive stars in close binaries. The disk accretion rate is typically super-Eddington and an ultrafast outflow with a velocity of ˜0.1-0.3 c will be launched into the circumstellar medium. The outflow forms a collisionless shock, and electrons are accelerated and emit synchrotron emission in radio bands with a flux of ˜ 10^{26-30} erg s^{-1} Hz^{-1} days to decades after the BH formation. The model predicts not only a fast UV/optical transient but also quasi-simultaneous inverse-Compton X-ray emission ˜ a few days after the BH formation, and the discovery of the radio counterpart with coordinated searches will enable us to identify this type of transients. The occurrence rate can be 0.1 - 10 % of the core-collapse supernova rate, which makes them a promising target of dedicated radio observations such as the Jansky VLA Sky Survey.

Blue optical continuum associated with a radio knot in 3C346

Science.gov (United States)

Dey, Arjun; van Breugel, Wil J. M.

1994-06-01

We report the discovery of extremely luminous near-UV continuum emission associated with a bright radio knot in the radio galaxy 3C346 (zeta = 0.162). Photometric measurements from U and r' band images and longslit spectra show a spectral energy distribution that steepens at higher frequencies, with radio and optical spectral indices alphar = -0.37 +/- 0.02 and alphao = -1.8 +/- 0.2, respectively. Based on a comparison of the optical properties of this knot with other known cases of optical emission associated with radio structures, we conclude that the continuum emission is optical synchrotron radiation. Our observations are consistent with the suggestion that 3C346 is a foreshortened FR-II radio galaxy with its radio axis oriented close to the line of sight. The optical and radio emission from the knot appear to be associated with a hotspot (at the end of a jet) on the near side. Finally, our U and r' images of 3C346 provide a striking illustration that the optical morphologies of nearby radio galaxies also depend upon wavelength and that studies of these objects are relevant to the interpretation of the alignment effect seen in the high redshift radio galaxies.

Diffuse interstellar gas in disk galaxies

International Nuclear Information System (INIS)

Vladilo, G.

1989-01-01

The physical properties of the diffuse gas in our Galaxy are reviewed and considered as a starting point for interstellar (IS) studies of disk galaxies. Attention is focussed on the atomic and ionic component, detected through radio, optical, ultraviolet (UV) and X-ray observations. The cooling and heating processes in the IS gas are briefly recalled in order to introduce current models of disk and halo gas. Observations of nearby galaxies critical to test IS models are considered, including 21-cm surveys, optical and UV absorptions of bright, extragalactic sources, and X-ray emission from hot halos. Finally, further steps necessary to develop a global model for the structure and evolution of the interstellar medium are indicated. (author)

Observation of quasi-periodic solar radio bursts associated with propagating fast-mode waves

Science.gov (United States)

Goddard, C. R.; Nisticò, G.; Nakariakov, V. M.; Zimovets, I. V.; White, S. M.

2016-10-01

Aims: Radio emission observations from the Learmonth and Bruny Island radio spectrographs are analysed to determine the nature of a train of discrete, periodic radio "sparks" (finite-bandwidth, short-duration isolated radio features) which precede a type II burst. We analyse extreme ultraviolet (EUV) imaging from SDO/AIA at multiple wavelengths and identify a series of quasi-periodic rapidly-propagating enhancements, which we interpret as a fast wave train, and link these to the detected radio features. Methods: The speeds and positions of the periodic rapidly propagating fast waves and the coronal mass ejection (CME) were recorded using running-difference images and time-distance analysis. From the frequency of the radio sparks the local electron density at the emission location was estimated for each. Using an empirical model for the scaling of density in the corona, the calculated electron density was used to obtain the height above the surface at which the emission occurs, and the propagation velocity of the emission location. Results: The period of the radio sparks, δtr = 1.78 ± 0.04 min, matches the period of the fast wave train observed at 171 Å, δtEUV = 1.7 ± 0.2 min. The inferred speed of the emission location of the radio sparks, 630 km s-1, is comparable to the measured speed of the CME leading edge, 500 km s-1, and the speeds derived from the drifting of the type II lanes. The calculated height of the radio emission (obtained from the density) matches the observed location of the CME leading edge. From the above evidence we propose that the radio sparks are caused by the quasi-periodic fast waves, and the emission is generated as they catch up and interact with the leading edge of the CME. The movie associated to Fig. 2 is available at http://www.aanda.org

Radio Observations of Gamma-ray Novae

Science.gov (United States)

Linford, Justin D.; Chomiuk, L.; Ribeiro, V.; project, E.-Nova

2014-01-01

Recent detection of gamma-ray emission from classical novae by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope surprised many in the astronomical community. We present results from radio observations, obtained using the Karl G. Jansky Very Large Array (VLA), of three gamma-ray novae: Mon2012, Sco2012, and Del2013. Radio observations allow for the calculation of ejecta masses, place limits on the distances, and provide information about the gamma-ray emission mechanism for these sources.

The Compact Radio Sources in the Nucleus of NGC 1068

Science.gov (United States)

Roy, A. L.; Colbert, E. J. M.; Wilson, A. S.; Ulvestad, J. S.

1998-09-01

We report VLBA images of the nucleus of the Seyfert galaxy NGC 1068 at 1.7, 5, and 15 GHz, with resolutions between 3 and 10 mas (0.2-0.7 pc) and a sensitivity of ~106 K at all three frequencies. Our goals are to study the morphology of the radio emission at subparsec resolution and to investigate thermal gas in the putative obscuring disk or torus and in the narrow-line region clouds through free-free absorption of the radio emission. All four known radio components in the central arcsecond (S2, S1, C, and NE, from south to north) have been detected at either 1.7 or 5 GHz, or both. No radio emission was detected at 15 GHz. Component S1 is probably associated with the active nucleus, with radio emission originating from the inner edge of the obscuring torus according to Gallimore et al. Our observed flux densities at 1.7 and 5 GHz are in agreement with their thermal bremsstrahlung emission model, and we find that the nuclear radiation may be strong enough to heat the gas in S1 to the required temperature of ~4 × 106 K. The bremsstrahlung power would be 0.15(frefl/0.01) times the bolometric luminosity of the nucleus between 1014.6 and 1018.4 Hz (where frefl is the fraction of radiation reflected into our line of sight by the electron-scattering mirror) and so the model is energetically reasonable. We also discuss two other models for S1 that also match the observed radio spectrum: electron scattering by the torus of radio emission from a compact synchrotron self-absorbed source and synchrotron radiation from the torus itself. Components NE and S2 have spectra consistent with optically thin synchrotron emission, without significant absorption. Both of these components are elongated roughly perpendicular to the larger scale radio jet, suggesting that their synchrotron emission is related to transverse shocks in the jet or to bow shocks in the external medium. Component C has a nonthermal spectrum absorbed at low frequency. This absorption is consistent with free

Radio halo sources in clusters of galaxies

International Nuclear Information System (INIS)

Hanisch, R.J.

1986-01-01

Radio halo sources remain one of the most enigmatic of all phenomena related to radio emission from galaxies in clusters. The morphology, extent, and spectral structure of these sources are not well known, and the models proposed to explain them suffer from this lack of observational detail. However, recent observations suggest that radio halo sources may be a composite of relic radio galaxies. The validity of this model could be tested using current and planned high resolutions, low-frequency radio telescopes. 31 references

Radio Observations of Ultra-Luminous X-Ray Sources and their Implication for Models

Science.gov (United States)

Koerding, E. G.; Colbert, E. J. M.; Falcke, H.

2004-05-01

We present the results of a radio monitoring campaign to search for radio emission from nearby ultra-luminous X-ray sources (ULXs). These intriguing sources are bright off-nuclear X-ray point sources with luminosities exceeding LX > 1039 erg/sec. Assuming isotropic emission the Eddington Limit suggests that they harbor intermediate mass black holes. Due to the problems of this explanation also other possibilities are currently discussed, among them are anisotropic emission, super-Eddington accretion flows or relativistically beamed emission from microquasars. Detections of compact radio cores at the positions of ULXs would be a direct hint to jet-emission. However, as the ULX phenomenom is connected to star formation we have to assume that they are strongly accreting objects. Thus, similar to their nearest Galactic cousins, the very high state X-ray binaries (see e.g., GRS 1915), ULXs may show radio flares. A well-defined sample of the 9 nearest ULXs has been monitored eight times during 5 months with the Very Large Array in A and B configuration. Our limiting sensitivity is 0.15 mJy (4 σ ) for flares and 68 μ Jy for continuous emission. In M82 some ULXs seem to be connected to radio supernova remnants. Besides that no flare or continuous emission has been detected. As the timescales of radio flares in ULXs are highly uncertain, it could well be that we have undersampled the lightcurve. However, upper bounds for the probability to detect a flare can be given. The upper limits for the continuous emission are compared with the emission found in NGC 5408 X-1 and with quasars and microquasars. We show that these limits are well in agreement with the microblazar model using the Radio/X-ray correlation of XRBs and AGN. Thus, it could well be that ULXs are microblazers which may be radio loud.

Planck Early Results. XV. Spectral Energy Distributions and Radio Continuum Spectra of Northern Extragalactic Radio Sources

Science.gov (United States)

Aatrokoski, J.; Ade, P. A. R.; Aghanim, N.; Aller, H. D.; Aller, M. F.; Angelakis, E.; Amaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.;

Diffusive emission of methane and carbon dioxide from two hydropower reservoirs in Brazil.

Science.gov (United States)

Marcelino, A A; Santos, M A; Xavier, V L; Bezerra, C S; Silva, C R O; Amorim, M A; Rodrigues, R P; Rogerio, J P

2015-05-01

The role of greenhouse gas emissions from freshwater reservoirs and their contribution to increase greenhouse gas concentrations in the atmosphere is currently under discussion in many parts of the world. We studied CO2 and CH4 diffusive fluxes from two large neotropical hydropower reservoirs with different climate conditions. We used floating closed-chambers to estimate diffusive fluxes of these gaseous species. Sampling campaigns showed that the reservoirs studied were sources of greenhouse gases to the atmosphere. In the Serra da Mesa Reservoir, the CH4 emissions ranged from 0.530 to 396.96 mg.m(-2).d(-1) and CO2 emissions ranged from -1,738.33 to 11,166.61 mg.m(-2).d(-1) and in Três Marias Reservoir the CH4 fluxes ranged 0.720 to 2,578.03 mg.m(-2).d(-1) and CO2 emission ranged from -3,037.80 to 11,516.64 to mg.m(-2).d(-1). There were no statistically significant differences of CH4 fluxes between the reservoirs, but CO2 fluxes from the two reservoirs studied were significantly different. The CO2 emissions measured over the periods studied in Serra da Mesa showed some seasonality with distinctions between the wet and dry transition season. In Três Marias Reservoir the CO2 fluxes showed no seasonal variability. In both reservoirs, CH4 emissions showed a tendency to increase during the study periods but this was not statistically significant. These results contributed to increase knowledge about the magnitude of CO2 and CH4 emission in hydroelectric reservoirs, however due to natural variability of the data future sampling campaigns will be needed to better elucidate the seasonal influences on the fluxes of greenhouse gases.

MODELING THE THERMAL DIFFUSE SOFT AND HARD X-RAY EMISSION IN M17

International Nuclear Information System (INIS)

Velázquez, P. F.; Rodríguez-González, A.; Esquivel, A.; Rosado, M.; Reyes-Iturbide, J.

2013-01-01

We present numerical models of very young wind driven superbubbles. The parameters chosen for the simulations correspond to the particular case of the M17 nebula, but are appropriate for any young superbubble in which the wind sources have not completely dispersed their parental cloud. From the simulations, we computed the diffuse emission in the soft ([0.5-1.5] keV) and hard ([1.5-5] keV) X-ray bands. The total luminosity in our simulations agrees with the observations of Hyodo et al., about two orders of magnitude below the prediction of the standard model of Weaver et al.. The difference with respect to the standard (adiabatic) model is the inclusion of radiative cooling, which is still important in such young bubbles. We show that for this type of object the diffuse hard X-ray luminosity is significant compared to that of soft X-rays, contributing as much as 10% of the total luminosity, in contrast with more evolved bubbles where the hard X-ray emission is indeed negligible, being at least four orders of magnitude lower than the soft X-ray emission.

Radio Imaging of Envelopes of Evolved Stars

Science.gov (United States)

Cotton, Bill

2018-04-01

This talk will cover imaging of stellar envelopes using radio VLBI techniques; special attention will be paid to the technical differences between radio and optical/IR interferomery. Radio heterodyne receivers allow a straightforward way to derive spectral cubes and full polarization observations. Milliarcsecond resolution of very bright, i.e. non thermal, emission of molecular masers in the envelopes of evolved stars can be achieved using VLBI techniques with baselines of thousands of km. Emission from SiO, H2O and OH masers are commonly seen at increasing distance from the photosphere. The very narrow maser lines allow accurate measurements of the velocity field within the emitting region.

Implications of the radio and X-ray emission that followed GW170817

Science.gov (United States)

Nakar, Ehud; Piran, Tsvi

2018-04-01

The radio and X-rays that followed GW170817 increased gradually over ˜ 100 days, resembling the radio flare predicted to arise from the interaction of a binary neutron star merger outflow with the ISM (Nakar & Piran 2011). Considering a blast wave moving with a Lorentz factor Γ, we show that an off-axis observer, namely an observer at θobs > 1/Γ, sees a light curve rising faster than Fν∝t3. Therefore, the observed rise, Fν∝ t0.78, implies that at all times we have seen an on-axis emission. Namely, the emitting matter was within θobs motivated one, proposed so far, is the interaction of a relativistic jet with the ejecta and the resulting cocoon. The jet could have been choked or successful. In the latter case, it has produced a short GRB pointing elsewhere (this successful jet-cocoon system is sometimes called a "structured jet"). Although circumstantial evidence disfavors a successful jet, the jet fate cannot be decisively determined from current observations. The light curve alone may not be sufficient to resolve this question, since both chocked and successful jets can lead to a gradual rise to a peak, followed by a decay. Therefore, the recent turnover of the light curve does not necessitate a successful jet.

A DEEP CHANDRA ACIS STUDY OF NGC 4151. II. THE INNERMOST EMISSION LINE REGION AND STRONG EVIDENCE FOR RADIO JET-NLR CLOUD COLLISION

International Nuclear Information System (INIS)

Wang Junfeng; Fabbiano, Giuseppina; Elvis, Martin; Risaliti, Guido; Karovska, Margarita; Zezas, Andreas; Mundell, Carole G.

2011-01-01

We have studied the X-ray emission within the inner ∼150 pc radius of NGC 4151 by constructing high spatial resolution emission line images of blended O VII, O VIII, and Ne IX. These maps show extended structures that are spatially correlated with the radio outflow and optical [O III] emission. We find strong evidence for jet-gas cloud interaction, including morphological correspondences with regions of X-ray enhancement, peaks of near-infrared [Fe II] emission, and optical clouds. In these regions, moreover, we find evidence of elevated Ne IX/O VII ratios; the X-ray emission of these regions also exceeds that expected from nuclear photoionization. Spectral fitting reveals the presence of a collisionally ionized component. The thermal energy of the hot gas suggests that ∼> 0.1% of the estimated jet power is deposited into the host interstellar medium through interaction between the radio jet and the dense medium of the circumnuclear region. We find possible pressure equilibrium between the collisionally ionized hot gas and the photoionized line-emitting cool clouds. We also obtain constraints on the extended iron and silicon fluorescent emission. Both lines are spatially unresolved. The upper limit on the contribution of an extended emission region to the Fe Kα emission is ∼< 5% of the total, in disagreement with a previous claim that 65% of the Fe Kα emission originates in the extended narrow line region.

The CO/NOx emissions of swirled, strongly pulsed jet diffusion flames

KAUST Repository

Liao, Ying-Hao

2014-05-28

The CO and NOx exhaust emissions of swirled, strongly pulsed, turbulent jet diffusion flames were studied experimentally in a coflow swirl combustor. Measurements of emissions were performed on the combustor centerline using standard emission analyzers combined with an aspirated sampling probe located downstream of the visible flame tip. The highest levels of CO emissions are generally found for compact, isolated flame puffs, which is consistent with the quenching due to rapid dilution with excess air. The imposition of swirl generally results in a decrease in CO levels by up to a factor of 2.5, suggesting more rapid and compete fuel/air mixing by imposing swirl in the coflow stream. The levels of NO emissions for most cases are generally below the steady-flame value. The NO levels become comparable to the steady-flame value for sufficiently short jet-off times. The swirled coflow air can, in some cases, increase the NO emissions due to a longer combustion residence time due to the flow recirculation within the swirl-induced recirculation zone. Scaling relations, when taking into account the impact of air dilution over an injection cycle on the flame length, reveal a strong correlation between the CO emissions and the global residence time. However, the NO emissions do not successfully correlate with the global residence time. For some specific cases, a compact flame with a simultaneous decrease in both CO and NO emissions compared to the steady flames was observed. © Copyright © Taylor & Francis Group, LLC.

Radio observations of the double-relic galaxy cluster Abell 1240

Science.gov (United States)

Hoang, D. N.; Shimwell, T. W.; van Weeren, R. J.; Intema, H. T.; Röttgering, H. J. A.; Andrade-Santos, F.; Akamatsu, H.; Bonafede, A.; Brunetti, G.; Dawson, W. A.; Golovich, N.; Best, P. N.; Botteon, A.; Brüggen, M.; Cassano, R.; de Gasperin, F.; Hoeft, M.; Stroe, A.; White, G. J.

2018-05-01

We present LOFAR 120 - 168 MHz images of the merging galaxy cluster Abell 1240 that hosts double radio relics. In combination with the GMRT 595 - 629 MHz and VLA 2 - 4 GHz data, we characterised the spectral and polarimetric properties of the radio emission. The spectral indices for the relics steepen from their outer edges towards the cluster centre and the electric field vectors are approximately perpendicular to the major axes of the relics. The results are consistent with the picture that these relics trace large-scale shocks propagating outwards during the merger. Assuming diffusive shock acceleration (DSA), we obtain shock Mach numbers of M=2.4 and 2.3 for the northern and southern shocks, respectively. For M≲ 3 shocks, a pre-existing population of mildly relativistic electrons is required to explain the brightness of the relics due to the high (>10 per cent) particle acceleration efficiency required. However, for M≳ 4 shocks the required efficiency is ≳ 1% and ≳ 0.5%, respectively, which is low enough for shock acceleration directly from the thermal pool. We used the fractional polarization to constrain the viewing angle to ≥53 ± 3° and ≥39 ± 5° for the northern and southern shocks, respectively. We found no evidence for diffuse emission in the cluster central region. If the halo spans the entire region between the relics (˜1.8 Mpc) our upper limit on the power is P1.4GHz = (1.4 ± 0.6) × 1023 W Hz-1 which is approximately equal to the anticipated flux from a cluster of this mass. However, if the halo is smaller than this, our constraints on the power imply that the halo is underluminous.

Characterizing X-Ray and Radio Emission in the Black Hole X-Ray Binary V404 Cygni During Quiescence

Science.gov (United States)

Rana, Vikram; Loh, Alan; Corbel, Stephane; Tomsick, John A.; Chakrabarty, Deepto; Walton, Dominic J.; Barret, Didier; Boggs, Steven E.; Christensen, Finn E.; Craig, William;

A Radio Study of the Ultra-luminous FIR Galaxy NGC 6240

Science.gov (United States)

Colbert, E.; Wilson, A. S.; Bland-Hawthorn, J.

1993-05-01

A number of galaxies observed in the IRAS mission are noted to emit ~ 99% of their bolometric flux in the FIR, with FIR luminosities in excess of 10(11) Lsun. The interacting galaxy NGC 6240 has often been referred to as the ``proto-typical'' ultra-luminous (L_FIR >~ 10(12) Lsun) FIR galaxy. The origin of the FIR excess remains a disputed subject in the literature. New observations of NGC 6240 were taken with the VLA at 20cm in the B-configuration, and at 3.6cm in the A-configuration. No significant radio emission was detected from or near the possible ultra-massive ``dark core'' hypothesized by Bland-Hawthorn et. al. (1991); however, approximately 30% of Seyfert galaxies have 20 cm radio luminosities weaker than the upper limit derived from the radio maps. The non-thermal radio emission from luminous FIR galaxies is tightly correlated with the FIR emission. Previous radio observations of NGC 6240 revealed two compact, steep-spectrum nuclear sources, nearly coincident with the two nuclear sources seen in optical images. The 2 images from the new VLA observations and 5 images from previous VLA observations are used to identify the morphological and spectral features of the strong, compact components in the nuclear regions (~ 3 kpc) from the nucleus. Feasible explanations for the radio emission are discussed. The models that have been proposed in the literature for the FIR excess of NGC 6240 are evaluated for consistency with the observed radio emission.

PRIFIRA: General regularization using prior-conditioning for fast radio interferometric imaging†

Science.gov (United States)

Naghibzadeh, Shahrzad; van der Veen, Alle-Jan

2018-06-01

Image formation in radio astronomy is a large-scale inverse problem that is inherently ill-posed. We present a general algorithmic framework based on a Bayesian-inspired regularized maximum likelihood formulation of the radio astronomical imaging problem with a focus on diffuse emission recovery from limited noisy correlation data. The algorithm is dubbed PRIor-conditioned Fast Iterative Radio Astronomy (PRIFIRA) and is based on a direct embodiment of the regularization operator into the system by right preconditioning. The resulting system is then solved using an iterative method based on projections onto Krylov subspaces. We motivate the use of a beamformed image (which includes the classical "dirty image") as an efficient prior-conditioner. Iterative reweighting schemes generalize the algorithmic framework and can account for different regularization operators that encourage sparsity of the solution. The performance of the proposed method is evaluated based on simulated one- and two-dimensional array arrangements as well as actual data from the core stations of the Low Frequency Array radio telescope antenna configuration, and compared to state-of-the-art imaging techniques. We show the generality of the proposed method in terms of regularization schemes while maintaining a competitive reconstruction quality with the current reconstruction techniques. Furthermore, we show that exploiting Krylov subspace methods together with the proper noise-based stopping criteria results in a great improvement in imaging efficiency.

Radio reconstruction of the mass of ultra-high cosmic rays

Energy Technology Data Exchange (ETDEWEB)

Dorosti, Qader [Institut fuer Kernphysik (IKP), KIT (Germany)

2015-07-01

Detection of ultra-high energy cosmic rays can reveal the processes of the most violent sources in the Universe, which yet has to be determined. Interaction of cosmic rays with the Earth's atmosphere results in cascades of secondary particles, i.e. air showers. Many of such particles are electrons and positrons. The induced electrons and positrons interact with the geomagnetic field and induce radio emissions. Detection of air showers along with the detection of induced radio emissions can furnish a precise measurement of the direction, energy and mass of ultra-high energy cosmic rays. The Auger Engineering Radio Array consists of 124 radio stations measuring radio emission from air showers, in order to reconstruct the energy, direction and mass of cosmic rays. In this contribution, we present a method which employs a reduced hyperbolic model to describe the shape of radio wave front. We have investigated that the parameters of the reduced hyperbolic model are sensitive to the mass of cosmic rays. The obtained results are presented in this talk.

Final report of fugitive and diffuse emissions evaluations at the Hanford Site, CY 1994

International Nuclear Information System (INIS)

Gleckler, B.P.; Schmidt, J.W.

1995-01-01

The objective of this study was to evaluate several of Hanford's major diffuse emission sources and evaluate the effectiveness of monitoring these sources individually versus collectively. The results from this evaluation may also be utilized to demonstrate Westinghouse's compliance status with the applicable air emissions regulations and determine if additional studies and/or evaluations are necessary. Air sampling results from four waste handling and storage facilities were collected for a one week period and analyzed. The following is a list of the selected sampling sites: Plutonium Finishing Plant; 241-BY Tank Farm; 1301-N Trench; 300 Area Trenches and North Ponds. These sites were chosen as being representative of most of the Hanford waste sites, which are known to be diffuse emission sites. The sites were evaluated on the following criteria: physical size, surface contamination levels, geology, vegetation density, surface cover, potential for occupational exposure, and potential for public exposure. The selected sites vary greatly with the selection criteria parameters, and as a result should provide representative data for most of Hanford's waste sites

Compact continuum radio sources in the Orion Nebula

International Nuclear Information System (INIS)

Garay, G.; Moran, J.M.; Reid, M.J.; European Southern Observatory, Garching, West Germany)

1987-01-01

The Orion Nebula was observed with the VLA in order to search for radio emission from compact H II regions indicative of embedded OB stars or from winds associated with pre-main sequence, low-mass stars. Fourteen of the 21 detected radio sources are within 30 arcsec of Omega 1 Orionis C; 13 of these objects are probably neutral condensations surrounded by ionized envelopes that are excited by the star. If the temperature of the ionized envelopes is 10,000 K and their electron densities decrease as the square of the distance from the core center, then a typical neutral condensation has a radius of 10 to the 15th cm and a peak electron density of 400,000/cu cm. Seven sources are in or near the Orion molecular cloud. Four of the sources have optical counterparts. Two are highly variable radio sources associated with X-ray sources, and two have radio spectra indicative of thermal emission. Two of the three optically invisible sources have radio emission likely to arise in a dense ionized envelope surrounding and excited by an early B-type star. 46 references

The Radio/Gamma-Ray Connection from 120 MHz to 230 GHz

Directory of Open Access Journals (Sweden)

Marcello Giroletti

2016-09-01

Full Text Available Radio loud active galactic nuclei are composed of different spatial features, each one characterized by different spectral properties in the radio band. Among them, blazars are the most common class of sources detected at gamma-rays by Fermi, and their radio emission is dominated by the flat spectrum compact core. In this contribution, we explore the connection between emission at high energy revealed by Fermi and at radio frequencies. Taking as a reference the strong and very highly significant correlation found between gamma rays and cm-λ radio emission, we explore the different behaviours found as we change the energy range in gamma rays and in radio, therefore changing the physical parameters of the zones involved in the emitted radiation. We find that the correlation weakens when we consider (1 gamma rays of energy above 10 GeV (except for high synchrotron peaked blazars or (2 low frequency radio data taken by the Murchison Widefield Array; on the other hand, the correlation strengthens when we consider mm-λ data taken by Atacama Large Millimeter Array (ALMA.

WEAK AND COMPACT RADIO EMISSION IN EARLY HIGH-MASS STAR-FORMING REGIONS. I. VLA OBSERVATIONS

Energy Technology Data Exchange (ETDEWEB)

Rosero, V.; Hofner, P. [Physics Department, New Mexico Tech, 801 Leroy Pl., Socorro, NM 87801 (United States); Claussen, M. [National Radio Astronomy Observatory, 1003 Lopezville Rd., Socorro, NM 87801 (United States); Kurtz, S.; Carrasco-González, C.; Rodríguez, L. F.; Loinard, L. [Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Morelia 58090, México (Mexico); Cesaroni, R. [INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze (Italy); Araya, E. D. [Physics Department, Western Illinois University, 1 University Circle, Macomb, IL 61455 (United States); Menten, K. M.; Wyrowski, F. [Max-Planck-Institute für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Ellingsen, S. P. [School of Physical Sciences, University of Tasmania, Private Bag 37, Hobart, Tasmania 7001 (Australia)

2016-12-01

We present a high-sensitivity radio continuum survey at 6 and 1.3 cm using the Karl G. Jansky Very Large Array toward 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 and 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 Very Large Array, this survey achieved map rms levels of ∼3–10  μ Jy beam{sup −1} at sub-arcsecond angular resolution. We extracted 70 continuum sources associated with 1.2 mm dust clumps. Most sources are weak, compact, and prime candidates for high-mass protostars. Detection rates of radio sources associated with the millimeter 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 and CMC–IRs occur close to the dust clump centers, with a median offset from it of 12,000 au and 4000 au, respectively. We calculated 5–25 GHz spectral indices using power-law fits and obtained a median value of 0.5 (i.e., flux increasing with frequency), suggestive of thermal emission from ionized jets. In this paper we describe the sample, observations, and detections. The analysis and discussion will be presented in Paper II.

The Nature of the Stingray Nebula from Radio Observations

Science.gov (United States)

Harvey-Smith, Lisa; Hardwick, Jennifer A.; De Marco, Orsola; Parthasarathy, Mudumba; Gonidakis, Ioannis; Akhter, Shaila; Cunningham, Maria; Green, James A.

2018-06-01

We have analysed the full suite of Australia Telescope Compact Array data for the Stingray planetary nebula. Data were taken in the 4- to 23-GHz range of radio frequencies between 1991 and 2016. The radio flux density of the nebula generally declined during that period, but between 2013 and 2016 it shows signs of halting that decline. We produced the first spatially resolved radio images of the Stingray nebula from data taken in 2005. A ring structure, which appears to be associated with the ring seen in HST images, was visible. In addition, we found a narrow extension to the radio emission towards the eastern and western edges of the nebula. We derived the emission measure of the nebula - this decreased between 1992 and 2011, suggesting that the nebula is undergoing recombination. The radio spectral index is broadly consistent with a free-free emission mechanism, however a single data point hints that a steeper spectral index has possibly emerged since 2013, which could indicate the presence of synchrotron emission. If a non-thermal component component has emerged, such as one associated with a region that is launching a jet or outflow, we predict that it would intensify in the years to come.

The Hartebeeshoek Radio Astronomy Observatory

International Nuclear Information System (INIS)

Nicolson, G.D.

1986-01-01

This article briefly discusses the questions, problems and study fields of the modern astronomer. Radioastronomy has made important contributions to the study of the evolution of stars and has given much information on the birth of stars while at the other extreme, studies of neutron stars and the radio emission from the remnants of supernova explosions have given further insight into the death of individual stars. Radio astronomical studies have learned astronomers much about the structure of the Milky way and some twenty years ago, in a search for new radio galaxies, quasars were discovered. Radioastronomy research in South Africa is carried out at the Hartebeesthoek Radio Astronomy Observatory

Radio detection of extensive air showers at the Pierre Auger Observatory

International Nuclear Information System (INIS)

Berat, C.

2013-01-01

The Pierre Auger Observatory explores the potential of radio-detection techniques to measure extensive air showers (EAS) induced by ultra-high energy cosmic rays. To study in detail the mechanisms responsible for radio emission in the MHz range, the Auger Engineering Radio Array has been installed at the Observatory. Presently consisting of 24 radio-detection stations, this number will grow to 150 units covering an area of almost 20 km 2 . Novel detection techniques based on the GHz emission from the EAS are currently being studied. AMBER (Air-shower Microwave Bremsstrahlung Experimental Radiometer) and MIDAS (Microwave Detection of Air Showers) are prototypes for a large imaging dish antenna. In EASIER (Extensive Air Shower Identification using Electron Radiometer), the microwave emission is detected by antenna horns located on each surface detector. MIDAS is a self-triggering system while AMBER and EASIER use the trigger from the Auger detectors to record the emission. The status of these radio-detection R and D efforts at the Pierre Auger Observatory will be reported

Radio detection of extensive air showers at the Pierre Auger Observatory

Energy Technology Data Exchange (ETDEWEB)

Berat, C., E-mail: berat@lpsc.in2p3.fr [LPSC, Université Joseph Fourier Grenoble 1, CNRS/IN2P3, Institut Polytechnique de Grenoble, 53 rue des Martyrs, 38000 Grenoble (France)

2013-08-01

The Pierre Auger Observatory explores the potential of radio-detection techniques to measure extensive air showers (EAS) induced by ultra-high energy cosmic rays. To study in detail the mechanisms responsible for radio emission in the MHz range, the Auger Engineering Radio Array has been installed at the Observatory. Presently consisting of 24 radio-detection stations, this number will grow to 150 units covering an area of almost 20 km{sup 2}. Novel detection techniques based on the GHz emission from the EAS are currently being studied. AMBER (Air-shower Microwave Bremsstrahlung Experimental Radiometer) and MIDAS (Microwave Detection of Air Showers) are prototypes for a large imaging dish antenna. In EASIER (Extensive Air Shower Identification using Electron Radiometer), the microwave emission is detected by antenna horns located on each surface detector. MIDAS is a self-triggering system while AMBER and EASIER use the trigger from the Auger detectors to record the emission. The status of these radio-detection R and D efforts at the Pierre Auger Observatory will be reported.

Coherent emission mechanisms in astrophysical plasmas

Science.gov (United States)

Melrose, D. B.

2017-12-01

Three known examples of coherent emission in radio astronomical sources are reviewed: plasma emission, electron cyclotron maser emission (ECME) and pulsar radio emission. Plasma emission is a multi-stage mechanism with the first stage being generation of Langmuir waves through a streaming instability, and subsequent stages involving partial conversion of the Langmuir turbulence into escaping radiation at the fundamental (F) and second harmonic (H) of the plasma frequency. The early development and subsequent refinements of the theory, motivated by application to solar radio bursts, are reviewed. The driver of the instability is faster electrons outpacing slower electrons, resulting in a positive gradient ({d}f(v_allel )/{d}v_allel >0) at the front of the beam. Despite many successes of the theory, there is no widely accepted explanation for type I bursts and various radio continua. The earliest models for ECME were purely theoretical, and the theory was later adapted and applied to Jupiter (DAM), the Earth (AKR), solar spike bursts and flare stars. ECME strongly favors the x mode, whereas plasma emission favors the o mode. Two drivers for ECME are a ring feature (implying {d}f(v)/{d}v>0) and a loss-cone feature. Loss-cone-driven ECME was initially favored for all applications. The now favored driver for AKR is the ring-feature in a horseshoe distribution, which results from acceleration by a parallel electric on converging magnetic field lines. The driver in DAM and solar and stellar applications is uncertain. The pulsar radio emission mechanism remains an enigma. Ingredients needed in discussing possible mechanisms are reviewed: general properties of pulsars, pulsar electrodynamics, the properties of pulsar plasma and wave dispersion in such plasma. Four specific emission mechanisms (curvature emission, linear acceleration emission, relativistic plasma emission and anomalous Doppler emission) are discussed and it is argued that all encounter difficulties. Coherent

POST-OUTBURST RADIO OBSERVATIONS OF THE HIGH MAGNETIC FIELD PULSAR PSR J1119-6127

Energy Technology Data Exchange (ETDEWEB)

Majid, Walid A.; Pearlman, Aaron B.; Dobreva, Tatyana; Kocz, Jonathon; Prince, Thomas A. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Horiuchi, Shinji [CSIRO Astronomy and Space Science, Canberra Deep Space Communications Complex, P.O. Box 1035, Tuggeranong, ACT 2901 (Australia); Lippuner, Jonas [TAPIR, Walter Burke Institute for Theoretical Physics, MC 350-17, California Institute of Technology, Pasadena, CA 91125 (United States)

2017-01-01

We have carried out high-frequency radio observations of the high magnetic field pulsar PSR J1119-6127 following its recent X-ray outburst. While initial observations showed no evidence of significant radio emission, subsequent observations detected pulsed emission across a large frequency band. In this Letter, we report on the initial disappearance of the pulsed emission and its prompt reactivation and dramatic evolution over several months of observation. The periodic pulse profile at S -band (2.3 GHz) after reactivation exhibits a multi-component emission structure, while the simultaneous X -band (8.4 GHz) profile shows a single emission peak. Single pulses were also detected at S -band near the main emission peaks. We present measurements of the spectral index across a wide frequency bandwidth, which captures the underlying changes in the radio emission profile of the neutron star. The high-frequency radio detection, unusual emission profile, and observed variability suggest similarities with magnetars, which may independently link the high-energy outbursts to magnetar-like behavior.

Radio core dominance of Fermi blazars

Science.gov (United States)

Pei, Zhi-Yuan; Fan, Jun-Hui; Liu, Yi; Yuan, Yi-Hai; Cai, Wei; Xiao, Hu-Bing; Lin, Chao; Yang, Jiang-He

2016-07-01

During the first 4 years of mission, Fermi/LAT detected 1444 blazars (3FGL) (Ackermann et al. in Astrophys. J. 810:14, 2015). Fermi/LAT observations of blazars indicate that Fermi blazars are luminous and strongly variable with variability time scales, for some cases, as short as hours. Those observations suggest a strong beaming effect in Fermi/LAT blazars. In the present work, we will investigate the beaming effect in Fermi/LAT blazars using a core-dominance parameter, R = S_{core}/ S_{ext.}, where S_{core} is the core emission, while S_{ext.} is the extended emission. We compiled 1335 blazars with available core-dominance parameter, out of which 169 blazars have γ-ray emission (from 3FGL). We compared the core-dominance parameters, log R, between the 169 Fermi-detected blazars (FDBs) and the rest non-Fermi-detected blazars (non-FDBs), and we found that the averaged values are R+(2.25±0.10), suggesting that a source with larger log R has larger V.I. value. Thirdly, we compared the mean values of radio spectral index for FDBs and non-FDBs, and we obtained < α_{radio}rangle =0.06±0.35 for FDBs and < α_{radio}rangle =0.57±0.46 for non-FDBs. If γ-rays are composed of two components like radio emission (core and extended components), then we can expect a correlation between log R and the γ-ray spectral index. When we used the radio core-dominance parameter, log R, to investigate the relationship, we found that the spectral index for the core component is α_{γ}|_{core} = 1.11 (a photon spectral index of α_{γ}^{ph}|_{core} = 2.11) and that for the extended component is α_{γ}|_{ext.} = 0.70 (a photon spectral index of α_{γ}^{ph}|_{ext.} = 1.70). Some discussions are also presented.

Simulation of radio nuclide migration in crystalline rock under influence of matrix diffusion and sorption kinetics: Code development and pre-assessment of migration experiment

International Nuclear Information System (INIS)

Woerman, A.; Xu Shulan

1996-04-01

The overall objective of the present study is to illuminate how spatial variability in rock chemistry in combination with spatial variability in matrix diffusion affects the radio nuclide migration along single fractures in crystalline rock. Models for ground water flow and transport of radio nuclides in a single fracture with micro-fissures have been formulated on the basis of generally accepted physical and chemical principles. Limits for the validity of the models are stated. The model equations are solved by combining finite differences and finite element methods in a computer code package. The computational package consists of three parts, namely, a stochastic field generator, a sub-program that solves the flow problem and a sub-program that solves the transport problem in a single fracture with connecting micro-fissures. Migration experiments have been pre-assessed by simulations of breakthrough curves for a constant concentration change at the upstream boundary. Breakthrough curves are sensitive to variations of parameters, such as, fracture aperture, porosity, distribution coefficient and advection velocity. The impact of matrix diffusion and sorption is manifested in terms of a retention of radionuclides causing a prolonged breakthrough. Heterogeneous sorption was characterized with a variable distribution coefficient for which the coefficient of variation CV(K d )=1 and the integral scale of an exponential covariance function is one tenth of the drill core's length. Simulated breakthrough curves for the heterogeneous sorption case have a relative variance of 3% in comparison to that of homogeneous case. An appropriate experimental set up for investigation of the effect of matrix diffusion and sorption on radio nuclide migration experiments would be an aperture less than 1 mm and porosity larger than 0.5%. 36 refs, 19 figs

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.

THE SPECTRUM OF ISOTROPIC DIFFUSE GAMMA-RAY EMISSION BETWEEN 100 MeV AND 820 GeV

Energy Technology Data Exchange (ETDEWEB)

Ackermann, M.; Buehler, R. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Ajello, M. [Department of Physics and Astronomy, Clemson University, Kinard Lab of Physics, Clemson, SC 29634-0978 (United States); Albert, A.; Blandford, R. D.; Bloom, E. D.; Bottacini, E.; Caliandro, G. A. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Atwood, W. B. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Baldini, L.; Bellazzini, R. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d' Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D.; Buson, S. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bechtol, K. [Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637 (United States); Bissaldi, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, and Università di Trieste, I-34127 Trieste (Italy); Brandt, T. J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bregeon, J. [Laboratoire Univers et Particules de Montpellier, Université Montpellier 2, CNRS/IN2P3, F-34095 Montpellier (France); Bruel, P., E-mail: markus.ackermann@desy.de, E-mail: bechtol@kicp.uchicago.edu [Laboratoire Leprince-Ringuet, École Polytechnique, CNRS/IN2P3, F-91128 Palaiseau (France); and others

2015-01-20

The γ-ray sky can be decomposed into individually detected sources, diffuse emission attributed to the interactions of Galactic cosmic rays with gas and radiation fields, and a residual all-sky emission component commonly called the isotropic diffuse γ-ray background (IGRB). The IGRB comprises all extragalactic emissions too faint or too diffuse to be resolved in a given survey, as well as any residual Galactic foregrounds that are approximately isotropic. The first IGRB measurement with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi) used 10 months of sky-survey data and considered an energy range between 200 MeV and 100 GeV. Improvements in event selection and characterization of cosmic-ray backgrounds, better understanding of the diffuse Galactic emission (DGE), and a longer data accumulation of 50 months allow for a refinement and extension of the IGRB measurement with the LAT, now covering the energy range from 100 MeV to 820 GeV. The IGRB spectrum shows a significant high-energy cutoff feature and can be well described over nearly four decades in energy by a power law with exponential cutoff having a spectral index of 2.32 ± 0.02 and a break energy of (279 ± 52) GeV using our baseline DGE model. The total intensity attributed to the IGRB is (7.2 ± 0.6) × 10{sup –6} cm{sup –2} s{sup –1} sr{sup –1} above 100 MeV, with an additional +15%/–30% systematic uncertainty due to the Galactic diffuse foregrounds.

Solar system radio astronomy at low frequencies

International Nuclear Information System (INIS)

Desch, M.D.

1987-01-01

The planetary radio-astronomy observations obtained with the two Voyager spacecraft since their launch in 1977 are briefly characterized and illustrated with graphs, diagrams, and sample spectra. Topics addressed include the spacecraft designs and trajectories, the wavelength coverage of the radio instruments, the Io-controlled LF emission of Jupiter, the solar-wind effect on the Saturn kilometric radiation, the Saturn electrostatic discharges, and the use of the clocklike feature of the Uranus emission to measure the planet's rotation period. 23 references

A transient, flat spectrum radio pulsar near the Galactic Centre

Science.gov (United States)

Dexter, J.; Degenaar, N.; Kerr, M.; Deller, A.; Deneva, J.; Lazarus, P.; Kramer, M.; Champion, D.; Karuppusamy, R.

2017-06-01

Recent studies have shown possible connections between highly magnetized neutron stars ('magnetars'), whose X-ray emission is too bright to be powered by rotational energy, and ordinary radio pulsars. In addition to the magnetar SGR J1745-2900, one of the radio pulsars in the Galactic Centre (GC) region, PSR J1746-2850, had timing properties implying a large magnetic field strength and young age, as well as a flat spectrum. All characteristics are similar to those of rare, transient, radio-loud magnetars. Using several deep non-detections from the literature and two new detections, we show that this pulsar is also transient in the radio. Both the flat spectrum and large amplitude variability are inconsistent with the light curves and spectral indices of three radio pulsars with high magnetic field strengths. We further use frequent, deep archival imaging observations of the GC in the past 15 yr to rule out a possible X-ray outburst with a luminosity exceeding the rotational spin-down rate. This source, either a transient magnetar without any detected X-ray counterpart or a young, strongly magnetized radio pulsar producing magnetar-like radio emission, further blurs the line between the two categories. We discuss the implications of this object for the radio emission mechanism in magnetars and for star and compact object formation in the GC.

A radio and optical study of Molonglo radio sources

Science.gov (United States)

Ishwara-Chandra, C. H.; Saikia, D. J.; McCarthy, P. J.; van Breugel, W. J. M.

2001-05-01

We present multi-wavelength radio observations with the Very Large Array, and narrow- and broad-band optical observations with the 2.5-m telescope at the Las Campanas Observatory, of a well-defined sample of high-luminosity Fanaroff-Riley class II radio galaxies and quasars, selected from the Molonglo Reference Catalogue 1-Jy sample. These observations were carried out as part of a programme to investigate the effects of orientation and environment on some of the observed properties of these sources. We examine the dependence of the Liu-Pooley relationship, which shows that radio lobes with flatter radio spectra are less depolarized, on size, identification and redshift, and show that it is significantly stronger for smaller sources, with the strength of the relationship being similar for both radio galaxies and quasars. In addition to Doppler effects, there appear to be intrinsic differences between the lobes on opposite sides. We discuss the asymmetry in brightness and location of the hotspots, and present estimates of the ages and velocities from matched-resolution observations in the L and C bands. Narrow- and broad-band optical images of some of these sources were made to study their environments and correlate with the symmetry parameters. An extended emission-line region is seen in a quasar, and in four of the objects possible companion galaxies are seen close to the radio axis.

A Measurement of the Millimeter Emission and the Sunyaev-Zel'dovich Effect Associated with Low-Frequency Radio Sources

Science.gov (United States)

Gralla, Megan B.; Crichton, Devin; Marriage, Tobias; Mo, Wenli; Aguirre, Paula; Addison, Graeme E.; Asboth, V.; Battaglia, Nick; Bock, James; Bond, J. Richard;

INVESTIGATING PARTICLE ACCELERATION IN PROTOSTELLAR JETS: THE TRIPLE RADIO CONTINUUM SOURCE IN SERPENS

Energy Technology Data Exchange (ETDEWEB)

Rodríguez-Kamenetzky, Adriana; Valotto, Carlos [Instituto de Astronomía Teórica y Experimental, (IATE-UNC), X5000BGR Córdoba (Argentina); Carrasco-González, Carlos; Rodríguez, Luis F. [Instituto de Radioastronomía y Astrofísica (IRyA-UNAM), 58089 Morelia, México (Mexico); Araudo, Anabella [University of Oxford, Astrophysics, Keble Road, Oxford OX1 3RH (United Kingdom); Torrelles, José M. [Institut de Ciències de l’Espai (CSIC-IEEC) and Institut de Ciències del Cosmos (UB-IEEC), Martí i Franquès 1, E-08028 Barcelona (Spain); Anglada, Guillem [Instituto de Astrofísica de Andalucía, CSIC, Camino Bajo de Huétor 50, E-18008 Granada (Spain); Martí, Josep [Dept. de Física, EPS de Jaén, Universidad de Jaén, Campus Las Lagunillas s/n, A3-402, E-23071 Jaén (Spain)

2016-02-10

While most protostellar jets present free–free emission at radio wavelengths, synchrotron emission has also been proposed to be present in a handful of these objects. The presence of nonthermal emission has been inferred by negative spectral indices at centimeter wavelengths. In one case (the HH 80-81 jet arising from a massive protostar), its synchrotron nature was confirmed by the detection of linearly polarized radio emission. One of the main consequences of these results is that synchrotron emission implies the presence of relativistic particles among the nonrelativistic material of these jets. Therefore, an acceleration mechanism should be taking place. The most probable scenario is that particles are accelerated when the jets strongly impact against the dense envelope surrounding the protostar. Here we present an analysis of radio observations obtained with the Very Large Array of the triple radio source in the Serpens star-forming region. This object is known to be a radio jet arising from an intermediate-mass protostar. It is also one of the first protostellar jets where the presence of nonthermal emission was proposed. We analyze the dynamics of the jet and the nature of the emission and discuss these issues in the context of the physical parameters of the jet and the particle acceleration phenomenon.

Radio observations of symbiotic stars

Energy Technology Data Exchange (ETDEWEB)

Wright, A E [Commonwealth Scientific and Industrial Research Organization, Epping (Australia). Div. of Radiophysics; Allen, D A

1978-09-01

A search for 2-cm continuum emission from 91 symbiotic stars has been undertaken using the Parkes radio telescope. Nine sources have been detected, four of which are reported for the first time. The radio spectral indices are mostly about + 0.6; these are interpreted in terms of mass loss. In two stars a portion of the radio spectrum has an index of zero, and for one of these stars (RX Puppis) this is plausibly a manifestation of the cessation of symbiotic activity that occurred about two decades ago. There is an extraordinarily good correlation between the detectability at 2cm and the presence of circumstellar dust, but not between the radio and optical domains. The importance of continued radio monitoring of HM Sagittae over the next few years is stressed.

`Zwicky's Nonet': a compact merging ensemble of nine galaxies and 4C 35.06, a peculiar radio galaxy with dancing radio jets

Science.gov (United States)

Biju, K. G.; Bagchi, Joydeep; Ishwara-Chandra, C. H.; Pandey-Pommier, M.; Jacob, Joe; Patil, M. K.; Kumar, P. Sunil; Pandge, Mahadev; Dabhade, Pratik; Gaikwad, Madhuri; Dhurde, Samir; Abraham, Sheelu; Vivek, M.; Mahabal, Ashish A.; Djorgovski, S. G.

2017-10-01

We report the results of our radio, optical and infrared studies of a peculiar radio source 4C 35.06, an extended radio-loud active galactic nucleus (AGN) at the centre of galaxy cluster Abell 407 (z = 0.047). The central region of this cluster hosts a remarkably tight ensemble of nine galaxies, the spectra of which resemble those of passive red ellipticals, embedded within a diffuse stellar halo of ˜1 arcmin size. This system (named 'Zwicky's Nonet') provides unique and compelling evidence for a multiple-nucleus cD galaxy precursor. Multifrequency radio observations of 4C 35.06 with the Giant Meterwave Radio Telescope (GMRT) at 610, 235 and 150 MHz reveal a system of 400-kpc scale helically twisted and kinked radio jets and outer diffuse lobes. The outer extremities of jets contain extremely steep-spectrum (spectral index -1.7 to -2.5) relic/fossil radio plasma with a spectral age of a few ×(107-108) yr. Such ultra-steep spectrum relic radio lobes without definitive hotspots are rare and they provide an opportunity to understand the life cycle of relativistic jets and physics of black hole mergers in dense environments. We interpret our observations of this radio source in the context of growth of its central black hole, triggering of its AGN activity and jet precession, all possibly caused by galaxy mergers in this dense galactic system. A slow conical precession of the jet axis due to gravitational perturbation between interacting black holes is invoked to explain the unusual jet morphology.

LOW-FREQUENCY OBSERVATIONS OF TRANSIENT QUASI-PERIODIC RADIO EMISSION FROM THE SOLAR ATMOSPHERE

Energy Technology Data Exchange (ETDEWEB)

Sasikumar Raja, K.; Ramesh, R., E-mail: sasikumar@iiap.res.in [Indian Institute of Astrophysics, II Block, Koramangala, Bangalore 560 034 (India)

2013-09-20

We report low-frequency observations of quasi-periodic, circularly polarized, harmonic type III radio bursts whose associated sunspot active regions were located close to the solar limb. The measured periodicity of the bursts at 80 MHz was ≈5.2 s, and their average degree of circular polarization (dcp) was ≈0.12. We calculated the associated magnetic field B (1) using the empirical relationship between the dcp and B for the harmonic type III emission, and (2) from the observed quasi-periodicity of the bursts. Both the methods result in B ≈ 4.2 G at the location of the 80 MHz plasma level (radial distance r ≈ 1.3 R{sub ☉}) in the active region corona.

Nanosecond radio bursts from strong plasma turbulence in the Crab pulsar.

Science.gov (United States)

Hankins, T H; Kern, J S; Weatherall, J C; Eilek, J A

2003-03-13

The Crab pulsar was discovered by the occasional exceptionally bright radio pulses it emits, subsequently dubbed 'giant' pulses. Only two other pulsars are known to emit giant pulses. There is no satisfactory explanation for the occurrence of giant pulses, nor is there a complete theory of the pulsar emission mechanism in general. Competing models for the radio emission mechanism can be distinguished by the temporal structure of their coherent emission. Here we report the discovery of isolated, highly polarized, two-nanosecond subpulses within the giant radio pulses from the Crab pulsar. The plasma structures responsible for these emissions must be smaller than one metre in size, making them by far the smallest objects ever detected and resolved outside the Solar System, and the brightest transient radio sources in the sky. Only one of the current models--the collapse of plasma-turbulent wave packets in the pulsar magnetosphere--can account for the nanopulses we observe.

Radio wave heating of the corona and electron precipitation during flares

Science.gov (United States)

Melrose, D. B.; Dulk, G. A.

1982-01-01

Electron-cyclotron masers, excited while energy release is occurring in a flaring magnetic loop, are likely to generate extremely intense radiation at decimeter wavelengths. The energy in the radiation can be comparable with that in the electrons associated with hard X-ray bursts, i.e., a significant fraction of the total energy in the flare. Essentially all of the radio energy is likely to be reabsorbed by gyroresonance absorption, either near the emitting region or at some distance away in neighboring loops. Enhanced diffusion of fast electrons caused by the maser can lead to precipitation at the maximum possible rate, and hence account for hard X-ray emission from the footpoints of the magnetic loops.

Determination of the ion thermal diffusivity from neutron emission profiles in decay

International Nuclear Information System (INIS)

Sasao, M.; Adam, J.M.; Conroy, S.; Jarvis, O.N.; Marcus, F.B.; Sadler, G.; Belle, P. van

1992-01-01

Spatial profiles of neutron emission are routinely obtained at the Joint European Torus (JET) from line-integrated emissivities measured with a multi-channel instrument. It is shown that the manner in which the emission profiles relax following termination of strong heating with Neutral Beam Injection (NBI) permits the local thermal diffusivity (χ i ) to be obtained with an accuracy of about 20%. The radial profiles of χ i for small minor radius (r/a 2 /s for H-mode plasmas with plasma current I p = 3.1 MA and toroidal field B T = 2.3T. The experimental value of χ i is smallest for Z eff = 2.2 and increases weakly with increasing Z eff . The experimental results disagree by two orders of magnitude with predictions from an ion temperature gradient driven turbulence model. (author) 6 refs., 3 figs

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...

X-ray continuum and iron K emission line from the radio galaxy 3C 390.3

Science.gov (United States)

Inda, M.; Makishima, K.; Kohmura, Y.; Tashiro, M.; Ohashi, T.; Barr, P.; Hayashida, K.; Palumbo, G. G. C.; Trinchieri, G.; Elvis, M.

1994-01-01

X-ray properties of the radio galaxy 3C 390.3 were investigated using the European X-ray Observatory Satellite (EXOSAT) and Ginga satellites. Long-term, large-amplitude X-ray intensity changes were detected over a period extending from 1984 through 1991, and high-quality X-ray spectra were obtained especially with Ginga. The X-ray continuum spectra were described with power-law model with photon slope in the range 1.5-1.8, and the slope flattened as the 2-20 keV luminosity decreased by 40%. There was a first detection of the iron emission line from this source at the 90% confidence level. An upper limit was derived on the thermal X-ray component. X-ray emission mechanisms and possible origins of the long-term variation are discussed.

MULTI-WAVELENGTH AFTERGLOWS OF FAST RADIO BURSTS

International Nuclear Information System (INIS)

Yi, Shuang-Xi; Gao, He; Zhang, Bing

2014-01-01

The physical origin of fast radio bursts (FRBs) is unknown. Detecting electromagnetic counterparts to FRBs in other wavelengths is essential to measure their distances and to determine their physical origin. Assuming that at least some of them are of cosmological origin, we calculate their afterglow light curves in multiple wavelengths (X-rays, optical, and radio) by assuming a range of total kinetic energies and redshifts. We focus on forward shock emission, but also consider the possibility that some of the FRBs might have bright reverse shock emission. In general, FRB afterglows are too faint to be detected by current detectors. Only if an FRB has a very low radiative efficiency in radio (hence, a very large kinetic energy), and when it is close enough to observe can its afterglow be detected in the optical and radio bands. We discuss observational strategies for detecting these faint afterglows using future telescopes such as Large Synoptic Survey Telescope and Expanded Very Large Array

LOFAR/H-ATLAS: the low-frequency radio luminosity-star formation rate relation

Science.gov (United States)

Gürkan, G.; Hardcastle, M. J.; Smith, D. J. B.; Best, P. N.; Bourne, N.; Calistro-Rivera, G.; Heald, G.; Jarvis, M. J.; Prandoni, I.; Röttgering, H. J. A.; Sabater, J.; Shimwell, T.; Tasse, C.; Williams, W. L.

2018-04-01

Radio emission is a key indicator of star formation activity in galaxies, but the radio luminosity-star formation relation has to date been studied almost exclusively at frequencies of 1.4 GHz or above. At lower radio frequencies, the effects of thermal radio emission are greatly reduced, and so we would expect the radio emission observed to be completely dominated by synchrotron radiation from supernova-generated cosmic rays. As part of the LOFAR Surveys Key Science project, the Herschel-ATLAS NGP field has been surveyed with LOFAR at an effective frequency of 150 MHz. We select a sample from the MPA-JHU catalogue of Sloan Digital Sky Survey galaxies in this area: the combination of Herschel, optical and mid-infrared data enable us to derive star formation rates (SFRs) for our sources using spectral energy distribution fitting, allowing a detailed study of the low-frequency radio luminosity-star formation relation in the nearby Universe. For those objects selected as star-forming galaxies (SFGs) using optical emission line diagnostics, we find a tight relationship between the 150 MHz radio luminosity (L150) and SFR. Interestingly, we find that a single power-law relationship between L150 and SFR is not a good description of all SFGs: a broken power-law model provides a better fit. This may indicate an additional mechanism for the generation of radio-emitting cosmic rays. Also, at given SFR, the radio luminosity depends on the stellar mass of the galaxy. Objects that were not classified as SFGs have higher 150-MHz radio luminosity than would be expected given their SFR, implying an important role for low-level active galactic nucleus activity.

Radio and X-Ray Observations of the 1998 Outburst of the Recurrent X-Ray Transient 4U 1630-47

Science.gov (United States)

Hjellming, R. M.; Rupen, M. P.; Mioduszewski, A. J.; Kuulkers, E.; McCollough, M.; Harmon, B. A.; Buxton, M.; Sood, R.; Tzioumis, A.; Rayner, D.; Dieters, S.; Durouchoux, P.

1999-03-01

We report radio (NRAO VLA and Australia Telescope Compact Array), soft X-ray (Rossi X-Ray Timing Explorer ASM), and hard X-ray (Compton Gamma Ray Observatory BATSE) observations of a 1998 outburst in the recurring X-ray transient 4U 1630-47, where radio emission was detected for the first time. The radio observations identify the position of 4U 1630-47 to within 1". Because the radio emission is optically thin with a spectral index of ~-0.8 during the rise, peak, and decay of the initial radio event, the emission is probably coming from an optically thin radio jet ejected over a period of time. The 20-100 keV emission first appeared 1998 January 28 (MJD 50841), the 2-12 keV emission first appeared 1998 February 3 (MJD 50847), and the first radio emission was detected 1998 February 12.6 (MJD 50856.6). The rise of the radio emission probably began about 1998 February 7 (MJD 50851) when the X-rays were in a very hard fluctuating-hardness state, just before changing to a softer, more stable hardness state.

Planck intermediate results: XVII. Emission of dust in the diffuse interstellar medium from the far-infrared to microwave frequencies

DEFF Research Database (Denmark)

Bartlett, J.G.; Cardoso, J.-F.; Delabrouille, J.

2014-01-01

H-atom. The dust temperature is observed to be anti-correlated with the dust emissivity and opacity. We interpret this result as evidence of dust evolution within the diffuse ISM. The mean dust opacity is measured to be (7.1 ± 0.6) × 10-27 cm2 H-1 × (v/353 GHz) 1.53 ± 0.03for 100 ≤ v ≤ 353 GHz......The dust-Hi correlation is used to characterize the emission properties of dust in the diffuse interstellar medium (ISM) from far infrared wavelengths to microwave frequencies. The field of this investigation encompasses the part of the southern sky best suited to study the cosmic infrared...... and microwave backgrounds. We cross-correlate sky maps from Planck, the Wilkinson Microwave Anisotropy Probe (WMAP), and the diffuse infrared background experiment (DIRBE), at 17 frequencies from 23 to 3000 GHz, with the Parkes survey of the 21 cm line emission of neutral atomic hydrogen, over a contiguous area...

A low-frequency radio survey of the planets with RAE 2

Science.gov (United States)

Kaiser, M. L.

1977-01-01

Over one thousand occultations of each planet in the solar system have occurred during the period from mid-1973 through mid-1976 as seen from the lunar orbiting Radio Astronomy Explorer 2 (RAE 2) spacecraft. These occultations have been examined for evidence of planetary radio emissions in the 0.025-13.1 MHz band. Only Jupiter and the earth have given positive results. Lack of detection of emission from the other planets can mean that either they do not emit radio noise in this band or the flux level of their emissions and/or its occurrence rate are too low to be detected by RAE 2.

A low-frequency radio survey of the planets with RAE-2

International Nuclear Information System (INIS)

Kaiser, M.L.

1976-08-01

Over one thousand occultations of each planet in the solar system have occurred during the period from mid-1973 through mid-1976 as seen from the lunar orbiting Radio Astronomy Explorer-2 (RAE-2) spacecraft. These occultations have been examined for evidence of planetary radio emissions in the 0.025 to 13.1 MHz band. Only Jupiter and the earth have given positive results. Lack of detection of emission from the other planets can mean that either they do not emit radio noise in this band or the flux level of their emissions and/or its occurrence rate are too low to be detected by RAE-2

A low-frequency radio survey of the planets with RAE-2

Science.gov (United States)

Kaiser, M. L.

1976-01-01

Over one thousand occultations of each planet in the solar system have occurred during the period from mid-1973 through mid-1976 as seen from the lunar orbiting Radio Astronomy Explorer-2 (RAE-2) spacecraft. These occultations have been examined for evidence of planetary radio emissions in the 0.025 to 13.1 MHz band. Only Jupiter and the earth have given positive results. Lack of detection of emission from the other planets can mean that either they do not emit radio noise in this band or the flux level of their emissions and/or its occurrence rate are too low to be detected by RAE-2.

A low-frequency radio survey of the planets with RAE 2

International Nuclear Information System (INIS)

Kaiser, M.L.

1977-01-01

Over one thousand occultations of each planet in the solar system have occurred during the period from mid-1973 through mid-1976 as seen from the lunar orbiting Radio Astronomy Explorer 2 (RAE 29) spacecraft. These occultations have been examined for evidence of planetary radio emissions in the 0.025--13.1 MHz band. Only Jupiter and the earth have given positive results. Lack of detection of emission from the other planets can mean that either they do not emit radio noise in this band or the flux level of their emissions and/or its occurrence rate are too low to be detected by RAE 2

Determination of the ion thermal diffusivity from neutron emission profiles in decay

International Nuclear Information System (INIS)

Sasao, M.; Adams, J.M.; Conroy, S.; Jarvis, O.N.; Marcus, F.B.; Sadler, G.; Belle, P. van

1994-01-01

Spatial profiles of the neutron emission from deuterium plasmas are routinely obtained at the Joint European Torus (JET) using the line-integrated signals measured with a multichannel instrument. It is shown that the manner in which these profiles relax following the termination of strong heating with neutral beam injection (NBI) permits the local thermal diffusivity (χ i ) to be obtained with an accuracy of about 20%. (author)