scholarly journals Spectral Index Versus Frequency and Models for the Continua of AGN and QSOs

1989 ◽  
Vol 134 ◽  
pp. 201-202
Author(s):  
Wayne A. Stein
Keyword(s):  
Accretion Disk ◽  
Spectral Index ◽  
Power Law ◽  
Spectral Distribution ◽  
Secondary Electron ◽  
Low Frequency ◽  
Spectral Indices ◽  
Ultraviolet Continuum ◽  
Electron Synchrotron ◽  
X Ray

The observed spectral index as a function of frequency of QSO continua must be explained in models. It is generally increasing (F(ν) ∝ ν−α, α increasing) with higher frequency in the infrared (downward curvature). The visual to ultraviolet continuum has been shown to be a broken power law with F(ν) ∝ ν−0.5 at low frequency and a break to larger α at νo ∼ 3×1015 Hz. X-ray observations frequently exhibit a flat continuum with α < 1. One prominent example is 3C273 for which α1–3μm → 2, αvis ∼ 0.5 and αx ∼ 0.5. These spectral indices arise naturally in Secondary Electron Synchrotron Self-Compton (SESSC) models. Some accretion disk models approach these spectral indices for the visual-ultraviolet portion of the spectral distribution.

scholarly journals A Comparison of the X-ray Spectra of Quasars and BL Lac Objects

1989 ◽  
Vol 134 ◽  
pp. 197-198
Author(s):  
D. M. Worrall ◽  
B. J. Wilkes
Keyword(s):  
Power Law ◽  
Radio Spectrum ◽  
Spectral Indices ◽  
Mean Power ◽  
Bl Lac Objects ◽  
X Ray ◽  
Bl Lac ◽  
Infrared Frequencies

Quasars with similar core-compact radio properties can be classified by their differences at optical and infrared frequencies. Their X-ray properties might be expected to be similar if the synchrotron self-Compton mechanism relates their radio and X-ray emission. We have compared the 0.2–3.5 keV mean power-law energy spectral indices, , for 4 quasar classes: 12 Highly Polarized QSOs (HPQs), 19 Flat Radio Spectrum, core-compact, low-polarization, QSOs (FRS QSOs), 24 radio-selected BL Lac objects, and 7 X-ray-selected BL Lac objects.

scholarly journals X-ray Properties of 3C 111: Separation of Primary Nuclear Emission and Jet Continuum

Universe ◽  
2020 ◽  
Vol 6 (11) ◽  
pp. 219
Author(s):  
Elena Fedorova ◽  
B.I. Hnatyk ◽  
V.I. Zhdanov ◽  
A. Del Popolo
Keyword(s):  
Accretion Disk ◽  
Power Law ◽  
Line Emission ◽  
High Energy ◽  
Power Law Model ◽  
X Ray ◽  
Additional Information ◽  
Observational Dataset ◽  
Simple Power ◽  
Photon Index

3C111 is BLRG with signatures of both FSRQ and Sy1 in X-ray spectrum. The significant X-ray observational dataset was collected for it by INTEGRAL, XMM-Newton, SWIFT, Suzaku and others. The overall X-ray spectrum of 3C 111 shows signs of a peculiarity with the large value of the high-energy cut-off typical rather for RQ AGN, probably due to the jet contamination. Separating the jet counterpart in the X-ray spectrum of 3C 111 from the primary nuclear counterpart can answer the question is this nucleus truly peculiar or this is a fake “peculiarity” due to a significant jet contribution. In view of this question, our aim is to estimate separately the accretion disk/corona and non-thermal jet emission in the 3C 111 X-ray spectra within different observational periods. To separate the disk/corona and jet contributions in total continuum, we use the idea that radio and X-ray spectra of jet emission can be described by a simple power-law model with the same photon index. This additional information allows us to derive rather accurate values of these contributions. In order to test these results, we also consider relations between the nuclear continuum and the line emission.

EFFECT OF BARIUM ON DIELECTRIC, FERROELECTRIC, IMPEDANCE AND ELECTRICAL MODULUS PROPERTIES OF Bi0.5Na0.5TiO3 CERAMICS

2011 ◽  
Vol 25 (22) ◽  
pp. 2931-2948 ◽  
Author(s):  
K. SAMBASIVA RAO ◽  
K. CH. VARADA RAJULU ◽  
B. TILAK
Keyword(s):  
Power Law ◽  
Single Phase ◽  
Low Frequency ◽  
Rhombohedral Structure ◽  
Conductivity Spectrum ◽  
X Ray ◽  
Impedance Spectroscopy Study ◽  
Conventional Sintering ◽  
Phase Compound ◽  
Jonscher’S Power Law

Perovskite structured ferroelectric ( Na 1/2 Bi 1/2)0.945 Ba 0.055 TiO 3 (BNBT-5.5) material has been synthesized by the conventional sintering technique. X-ray analysis on the material showed a single phase compound with rhombohedral structure with lattice parameters a = 3.89 Åand α = 89.893 Å. Frequency and temperature dependence of dielectric permittivity, impedance, modulus and conductivity have been performed in the frequency and temperature range 45 Hz–5 MHz and 35–595°C, respectively. The observed low frequency dielectric dispersion (LFDD) in the material could be explained by Jonschers power law and evaluated activation energies at different temperature regions. Impedance spectroscopy study showed the presence of both bulk and grain boundary effects in the materials. The ac conductivity spectrum obeyed the Jonscher's power law. Modulus analysis indicated the possibility of hopping mechanism for electrical process in the system.

scholarly journals Spectral Index - Redshift Relation for Radio Galaxies and Quasars

1996 ◽  
Vol 175 ◽  
pp. 569-570
Author(s):  
R.D. Dagkesamanskii
Keyword(s):  
Flux Density ◽  
Spectral Index ◽  
Low Frequency ◽  
Radio Galaxies ◽  
Cosmological Evolution ◽  
Radio Sources ◽  
Spectral Indices ◽  
Extragalactic Radio Sources

Cosmological evolution of synchrotron spectra of the powerful extragalactic radio sources was studied by many authors. Some indications of such an evolution had been found firstly by analysis of ‘spectral index - flux density’ (α – S) relation for the sample of relatively strong radio sources. Later Gopal-Krishna and Steppe extended the analysis to weaker sources and found that the slope of αmed(S) curve changes dramatically at intermediate flux densities. Gopal-Krishna and Steppe pointed out that the maxima of the αmed(S) curve and of differential source counts are at almost the same flux density ranges (see, Fig. 2). It has to be noticed that the all mentioned results were obtained using the low-frequency spectral indices and on the basis of low frequency samples.

scholarly journals Hybrid Accretion-Disks in AGN and the AGN Contribution to the XRB

1994 ◽  
Vol 159 ◽  
pp. 491-491
Author(s):  
Amri Wandel
Keyword(s):  
Accretion Disk ◽  
Accretion Disks ◽  
Power Law ◽  
Accretion Rate ◽  
Bremsstrahlung Spectrum ◽  
Spectral Evolution ◽  
X Ray ◽  
X Ray Background ◽  
Inner Region ◽  
Two Temperature

The hybrid accretion-disk (HAD) model links the two characteristic components of AGN spectra – the UV bump and the X-ray power-law – in the framework of one physical model. The radially stratified hybrid disk is a self consistent combination of a thin, cool accretion disk at large radii, with an inner hot two-temperature disk. Its spectrum consists of three components, corresponding to the three radial disk regions: a blackbody thermal spectrum from the outer cool disk, a Comptonized soft photon power-law spectrum from the intermediate region, and a thermal Comptonized bremsstrahlung spectrum from the inner region. The dependence of the hybrid disk spectrum on the accretion rate and on other parameters is discussed and applied to AGN spectral evolution, and in particular to explaining the cosmic X-ray background by AGN.

scholarly journals Deep GMRT 610 MHz observations of the ELAIS N1 field: catalogue and source counts

2019 ◽  
Vol 491 (1) ◽  
pp. 1127-1145 ◽  
Author(s):  
E F Ocran ◽  
A R Taylor ◽  
M Vaccari ◽  
C H Ishwara-Chandra ◽  
I Prandoni
Keyword(s):  
Spectral Index ◽  
Low Frequency ◽  
Source Population ◽  
X Ray ◽  
Star Forming ◽  
Density Distributions ◽  
Deep Image ◽  
Frequency Source ◽  
Minimum Noise ◽  
Good Agreement

ABSTRACT This is the first of a series of papers based on sensitive 610 MHz observations of the ELAIS N1 field, using the Giant Metrewave Radio Telescope. We describe the observations, processing and source catalogue extraction from a deep image with area of 1.86 deg2 and minimum noise of ∼7.1 μJy beam−1. We compile a catalogue of 4290 sources with flux densities in the range of 28.9 μJy– 0.503 Jy and derive the Euclidean-normalized differential source counts for sources with flux densities brighter than $\rm {35.5\, \mu Jy}$. Our counts show a flattening at 610 MHz flux densities below 1 mJy. Below the break the counts are higher than previous observations at this frequency, but generally consistent with recent models of the low-frequency source population. The radio catalogue is cross-matched against multiwavelength data leading to identifications for 92 per cent and reliable redshifts for 72 per cent of our sample, with 19 per cent of the redshifts based on spectroscopy. For the sources with redshifts, we use radio and X-ray luminosity, optical spectroscopy and mid-infrared colours to search for evidence of the presence of an active galactic nucleus (AGN). We compare our identifications to predictions of the flux density distributions of star-forming galaxies (SFGs) and AGN, and find a good agreement assuming the majority of the sources without redshifts are SFGs. We derive spectral index distributions for a sub-sample. The majority of the sources are steep spectra, with a median spectral index that steepens with frequency: $\mathrm{\alpha ^{610}_{325}\, =\, -0.80\, \pm \, 0.29}$, $\mathrm{\alpha ^{610}_{1400}\, =\, -0.83\, \pm \, 0.31}$, and $\mathrm{\alpha ^{610}_{5000}\, =\, -1.12\, \pm \, 0.15}$.

scholarly journals Number Counts and Spectral Distribution of Radio Sources at Centimeter Wavelengths

1972 ◽  
Vol 44 ◽  
pp. 444-452 ◽  
Author(s):  
I. I. K. Pauliny-Toth ◽  
K. I. Kellermann ◽  
M. M. Davis
Keyword(s):  
Flux Density ◽  
Spectral Index ◽  
Excellent Agreement ◽  
Spectral Distribution ◽  
Low Frequency ◽  
Systematic Change ◽  
Radio Sources ◽  
Significant Dependence ◽  
5 Ghz ◽  
Number Counts

The results of a survey of selected regions of sky made at a frequency of 5 GHz, and of measurements of the spectral index distributions for sources selected from low frequency surveys are presented. The source counts and spectral distribution at 5 GHz are in excellent agreement with those expected from surveys made at lower frequencies. There is no significant dependence of the spectral distribution on flux density in any of the surveys we have investigated, implying either a low redshift for the sources, or a systematic change in their properties with redshift.

scholarly journals On the frequency correlations of low-frequency QPOs with kilohertz QPOs in accreting millisecond X-ray pulsars

2019 ◽  
Vol 490 (4) ◽  
pp. 5270-5284 ◽  
Author(s):  
Marieke van Doesburgh ◽  
Michiel van der Klis
Keyword(s):  
Black Hole ◽  
Power Law ◽  
Equations Of State ◽  
Low Frequency ◽  
Data Sets ◽  
Periodic Oscillations ◽  
X Ray ◽  
Frame Dragging ◽  
Low Mass ◽  
X Ray Binaries

ABSTRACT We investigate frequency correlations of low frequency (LF, &lt;80 Hz) and kHz quasi-periodic oscillations (QPOs) using the complete RXTE data sets on six accreting millisecond X-ray pulsars (AMXPs) and compare them to those of non-pulsating neutron star (NS) low-mass X-ray binaries with known spin. For the AMXPs SAX J1808.4−3658 and XTE J1807−294, we find frequency-correlation power-law indices that, surprisingly, are significantly lower than in the non-pulsars, and consistent with the relativistic precession model (RPM) prediction of 2.0 appropriate to test-particle orbital and Lense–Thirring precession frequencies. As previously reported, power-law normalizations are significantly higher in these AMXPs than in the non-pulsating sources, leading to requirements on the NS specific moment of inertia in this model that cannot be satisfied with realistic equations of state. At least two other AMXPs show frequency correlations inconsistent with those of SAX J1808.4−3658 and XTE J1807−294, and possibly similar to those of the non-pulsating sources; for two AMXPs no conclusions could be drawn. We discuss these results in the context of a model that has had success in black hole (BH) systems involving a torus-like hot inner flow precessing due to (prograde) frame dragging, and a scenario in which additional (retrograde) magnetic and classical precession torques not present in BH systems are also considered. We show that a combination of these interpretations may accommodate our results.

scholarly journals Variation of the Solar Flare Energy Spectrum Over the 11-Year Activity Cycle

1989 ◽  
Vol 104 (2) ◽  
pp. 255-258 ◽  
Author(s):  
V.V. Kasinsky ◽  
R.T. Sotnikova
Keyword(s):  
Energy Spectrum ◽  
Solar Flare ◽  
Spectral Index ◽  
Power Law ◽  
Activity Cycle ◽  
Energy Spectra ◽  
Cycle Phase ◽  
X Ray ◽  
Flux Data ◽  
Flare Energy

AbstractBased on X-ray (1-8 Å) flux data for 1977-1987, the integral spectra of solar flare energy were computed. The energy spectra were approximated by a power law N(E) α; E~n, with N being the number of flares with energy in excess of E. It is shown that the spectral index (β) varies systematically with the 11-year cycle phase.

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