Synchrotron Origin Research Articles

VLBI observations of the quasars CTD20 (0234+285), OJ248 (0827+243), and 4C19.44 (1354+195), and the millimeter-X-ray connection

We have obtained limited VLBI data on the quasars CTD20, OJ248, and 4C19.44 at 2.8 cm. CTD20 was also observed at 6 and 18 cm. All three sources contain multicomponent structure, and rather large fractions of the 2.8-cm flux densities arise in unresolved regions. All of the radio flux density of CTD20 originates in compact components. 4C19.44 is dominated at low frequencies by a steep-spectrum component which exceeds about 7 mas in size. Above 2 GHz the spectrum is flat and variable owing to several compact components. CTD20 and OJ248 belong to a sample of millimeter-excess quasars which were shown by Owen, Helfand, and Spangler to have highly predictable ratios of 90 GHz to 2-keV flux densities. A self-Compton explanation of this relationship is supported by the existence of unresolved radio components. However, the rapid 90-GHz variability of OJ248 and other quasars with strong millimeter emission should destroy the observed tight correlation except under special circumstances. A synchrotron origin of the radio-to-x-ray emission requires that any variations in the radio should be time delayed relative to the x ray.

X-ray spectral classification of supernova remnants in the Large Magellanic Cloud

The solid state spectrometer on the Einstein Observatory was used to measure the 0.6-4.5 keV X-ray spectra of six prominent supernova remnants in the Large Magellanic Cloud, namely, N132D, N63A, N49, 0525-66.0, N157B, and 0540-69.3. Thermal emission is detected from the first four remnants and is similar in nature to that observed from young galactic SNRs. In contrast, N157B and 0540-69.3 have featureless X-ray spectra which are well described by power-law models. The present data support a synchrotron origin for the X-rays from N157B and 0540-69.3, although an alternative emission mechanism is considered for the latter object.

Coordinated photometric and spectroscopic observations of strong extragalactic 90 GHz sources

Nearly simultaneous radio and infrared-optical observations were obtained for several extragalactic radio sources which are strong at 90 GHz. The spectral-flux distributions are generally peaked or flat over the radio portion of the spectrum with a steeper, power-law behavior at infrared-optical frequencies. For all sources, the radio and infrared-optical portions of the spectral-flux distributions can be smoothly joined by physically sensible interpolations over the spectral gap, although spectral breaks are required. For many of the sources, this is consistent with a common (synchrotron) origin of the radio, millimeter, and infrared-optical radiation. However, proof, in terms of correlated temporal variations and polarization properties, is still generally lacking.

Imaging polarimetry of the jets of M87 and 3C 273

Photoelectric polarization maps of the jets associated with M87 and 3C 273 are presented. For the M87 jet, polarization of individual knots reaches 20%. Comparison of the complex position angle structures at optical and radio frequencies (i) indicates the presence of a uniform (scale length> or approx. =1.5 kpc) medium in the vicinity of M87 which causes a Faraday rotation along the line of sight greater than approx.360rad m/sup -2/, and (ii) places an upper limit on the amount of Faraday depolarization occurring within individual knots.For the 3C 273 jet as a whole, our observations yield P=3.7% +- 4.1%. This measurement is consistent with inverse Compton models of the optical emission; however, a synchrotron origin cannot be excluded if the small-scale structure of the 3C 273 jet is similar to that of the jet of M87.

Evidence for the Softening of the Cosmic-Ray Electron Spectrum at a Few Hundred GeV and the Origin of the Galactic Ridge X-Radiation

In addition to the standard arguments based on storage lifetime, we show that data from muon-poor Earth air showers also independently indicate that the cosmic-ray electron spetrum does soften at a few hundred GeV. This situation rules out theories of a synchrotron origin for the diffuse galactic X-rays. A two-component theory is suggested for the X-rays with an inverse Compan contribution and a discrete, unresolved source contribution. (auth)

Long-term variations of total and polarized fluxes, absolute energy distribution, and line strength of BL Lac and 4 quasi-stellar sources.

view Abstract Citations (74) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Long-term variations of total and polarized fluxes, absolute energy distribution, and line strength of BL Lacertae and four quasi-stellar sources. Visvanathan, N. Abstract Observations of blue magnitude, polarization, wavelength dependence of polarization, absolute energy distribution of the continuum, and the strength of emission lines were obtained simultaneously for the variable QSSs 3C 279, 3C 345, 3C 446, 3C 454.3, and the object BL Lacertae on several occasions during the period 1967-1970. The continuum was linearly polarized in all these objects during outburst and nonoutburst periods and also when the objects reached minimum brightness. Whenever the total flux increased, an increase in polarized flux was observed. The position angle of the electric vector changed during the burst. The ratio between the polarized flux and the total flux does not exceed the value of about 0.16. This low value is interpreted as being due to the resultant polarization caused by several active spots in the continuum emitting-region. The absolute energy distributions of the continua both in active and quiet periods show that a power4aw representation of the continuum is valid. This fact and the finding that the polarization is independent of wavelength support the view that the radiation in these objects in the observed frequency range is of synchrotron origin in both active and quiet periods. Variations in the spectral index of the continua were observed, but no simple relationship between color and brightness was found. During the period of our observations the absolute intensity of the emission line Mg ii in 3C 345 and 3C 434.3, and the C iv line in 3C 446, remained constant within 1020 percent. The emission line Mg ii in 3C 345 was unpolarized, indicating that the regions from which the emission line originates are randomly arranged. Subject headings: polarization - quasi-stellar sources or objects Publication: The Astrophysical Journal Pub Date: January 1973 DOI: 10.1086/151842 Bibcode: 1973ApJ...179....1V full text sources ADS | data products SIMBAD (1) NED (1)

The nature of radio emission from pulsars

It is shown that radio emission from pulsars is unlikely to be of coherent synchrotron origin if the surface magnetic field of the central neutron star is greater than 108 G.

A Blast-Wave Model for the VELA X Supernova Remnant and the Origin of the GUM Nebula

view Abstract Citations (27) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Blast-Wave Model for the VELA X Supernova Remnant and the Origin of the GUM Nebula Tucker, Wallace H. Abstract The origin of the radio and X-ray emission from Vela X is discussed. The X-ray observations can be interpreted in terms of thermal radiation from a blast wave produced by the supernova explosion that formed Vela X. For an appropriate choice of parameters, the total power radiated by the shock wave is sufficient to explain the ionization in the Gum Nebula. The radio emission can be explained in terms of synchrotron radiation from relativistic electrons interacting with the region of high magnetic field behind the shock front. The pulsar in Vela X must have been about 100 times more active in the past in order to explain the energy content in relativistic electrons. A synchrotron origin for the X-ray emission is also possible. It should be possible to prove or disprove the thermal model by means of highresolution X-ray observations and perhaps by the observation of coronal iron-line emission. Publication: The Astrophysical Journal Pub Date: August 1971 DOI: 10.1086/180766 Bibcode: 1971ApJ...167L..85T full text sources ADS |

Gamma radiation from the celestial X-ray source sco X-1

Gamma radiation from the X-ray sources Sco X-1 due to Comptonsynchrotron process is calculated. Comparison with the upper limits set by an experimental survey for sources of gamma-rays with energy greater than 100 MeV has been made and constraints on the size of the source and its magnetic field are discussed. The flux predicted in the energy range 1011–1012 eV is above the observable lower limit of presentday detectors. An observation of this flux will serve as a test of the synchrotron origin of the X-radiation.

Colors, Linear Polarization, and Preliminary Mapping of the Magnetic Field for the Outer Filaments in the Exploding Galaxy M82

view Abstract Citations (27) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Colors, Linear Polarization, and Preliminary Mapping of the Magnetic Field for the Outer Filaments in the Exploding Galaxy M82 Sandage, Allan ; Visvanathan, N. Abstract The surface brightness, colors, and linear polarization of selected regions in the outer filaments of M82 have been measured in optical wavelengths. The measured filaments are very faint, ranging in surface brightness from V = 22.4 to V = 25.0 mag per square second of arc. The (U - B, B - V)-colors are much bluer than the main body of M82. Theoretical colors, calculated from a synchrotron spectrum that passes through the radio data and that extends into the optical region, generally agree with the observed colors to within z~ log F(~) = ±003 if the high-frequency cutoff is put between 4 X IOF~ and 6 X 1O'~ Hz. Large linear polarization is present for each region and reaches a maximum value of 32 percent for patch J. The direction of the electric vector is perpendicular to the two main filaments on the north side of M82. The electric vectors form a somewhat less regular pattern on the south side, but agree sufficiently in direction to show that the magnetic field lies predominantly along the minor axis of M82 if the radia- tion is of synchrotron origin. The data support, but do not prove, the hypothesis that the large-scale filaments are emitting optical synchrotron radiation caused by relativistic electrons whose energies reach ~ X 1012 eV if the average magnetic field strength is between 1O~ and 10-6 gauss Publication: The Astrophysical Journal Pub Date: September 1969 DOI: 10.1086/150136 Bibcode: 1969ApJ...157.1065S full text sources ADS | data products NED (1)

Association of centimeter-wave bursts with different spectral types of meter-wave bursts of solar radio emission

It is shown that about 40 per cent of 10.7 cm-λ bursts with peak intensities greater than 5×10−22 wm−2 (c/s)−1 are accompanied by bursts on meter waves. The percentage association increases with the peak intensity of 10.7 cm-λ bursts and attains a value of about 90 per cent when the peak intensity exceeds 1000×10−22 wm−2 (c/s)−1. The reverse association, that is, the association of a meter-λ burst with a burst on centimeter waves, is dependent on the spectral type of the meter-λ burst. The association is about 15, 40, 70, and 100 per cent for types III, V, II, and IV, respectively. The type III and type V bursts usually occur within about 1 minute and ½ minute, respectively, of the associated cm-λ burst maxima. The type II bursts occur after about 2 to 6 minutes of the associated cm-λ burst maxima. The type IV bursts in the 250 to 580 Mc/s range occur within about 4 minutes of the start of the associated cm-λ bursts. From simultaneous dynamic spectral observations in the 25 to 580 Mc/s range and single-frequency observations on 9400, 3750, 2000, and 1000 Mc/s, the average spectra of cm-λ bursts associated with different spectral types of meter-λ bursts have been studied. It is shown that cm-λ bursts associated with meter-λ type IV and type II bursts have brightness temperatures of the order of 108 and 107 deg K, respectively, and can probably be explained by synchrotron radiation of high-energy electrons. The cm-λ bursts associated with type V and type III bursts have brightness temperatures of 106 to 107 deg K in the 2000 to 9400 Mc/s range and have probably a thermal plus synchrotron origin; the 1000 Mc/s bursts have brightness temperatures higher than 107 deg K and have a nonthermal origin, probably due to plasma oscillation corresponding to type III bursts. The cm-λ bursts unaccompanied by any meter-λ burst have brightness temperatures less than 106 deg K and are believed to have a thermal origin.