scholarly journals The X-ray Spectral Properties for Gamma-ray Loud Blazars

2003 ◽  
Vol 214 ◽  
pp. 299-302
Author(s):  
Ben-Zhong Dai
Keyword(s):  
Correlation Analysis ◽  
Gamma Ray ◽  
X Rays ◽  
Spectral Indices ◽  
Bl Lac Objects ◽  
X Ray ◽  
Weighted Analysis ◽  
Spectrum Radio ◽  
Γ Ray ◽  
Weighted Correlation

We selected a sample of bright γ-ray (E>100 MeV) blazars whose X-rays in 0.1–10.0 keV band are observed by ROSAT and other X-ray satellites, and make a detailed spectral analysis between the soft (0.1–2.0 keV) and hard band (2.0–10.0keV) as well as between X-ray and γ-ray properties using both un-weighted and weighted analysis methods. Our results indicate: (i) there are significant anti-correlations of the spectral indices between soft X-rays and γ-rays, and between hard X-ray and γ-ray of flat-spectrum radio quasars (FSRQs) and BL Lac objects; (ii) in the X-ray band, the correlation is confusing, there is positive correlation of the spectral indices between soft and hard X-ray band using weighted correlation analysis, but this correlation is negative using un-weighted correlation analysis.

scholarly journals Gamma-ray-emitting narrow-line Seyfert 1 galaxies: the Swift view

2020 ◽  
Vol 496 (2) ◽  
pp. 2213-2229 ◽  
Author(s):  
F D’Ammando
Keyword(s):  
Gamma Ray ◽  
Thermal Emission ◽  
Optical Emission ◽  
X Rays ◽  
Narrow Line ◽  
X Ray ◽  
Relativistic Jet ◽  
Photon Index ◽  
Γ Ray ◽  
Lower Variability

ABSTRACT We report the analysis of all Swift observations available up to 2019 April of γ-ray-emitting narrow-line Seyfert 1 galaxies (NLSy1). The distribution of X-ray luminosities (and fluxes) indicates that the jet radiation significantly contributes to their X-ray emission, with Doppler boosting making values higher than other radio-loud NLSy1. The 0.3–10 keV photon indices are on average harder with respect to radio-quiet and radio-loud NLSy1, confirming a dominant jet contribution in X-rays. However, the lower variability amplitude with respect to blazars and the softening of the spectrum in some periods suggests that also the corona radiation contributes to the X-ray emission. In optical and ultraviolet (UV) significant flux changes have been observed on daily, weekly, and monthly time-scale, providing a clear indication of the significant contribution of the jet radiation in this part of spectrum. A strong correlation between X-ray, UV, and optical emission and simultaneous flux variations have been observed in 1H 0323+342, SBS 0846+513, PMN J0948+0022 as expected in case the jet radiation is the dominant mechanism. Correlated multiband variability favours the jet-dominated scenario also in FBQS J1644+2619 and PKS 2004−447. The summed X-ray Telescope spectra of 1H 0323+342, SBS 0846+513, PMN J0948+0022, and FBQS J1644+2619 are well fitted by a broken power law with a break around 2 keV. The spectrum above 2 keV is dominated by the non-thermal emission from a beamed relativistic jet, as suggested by the hard photon index. A Seyfert-like feature like the soft X-ray excess has been observed below 2 keV, making these γ-ray-emitting NLSy1 different from typical blazars.

scholarly journals Spectral Properties of Fermi Blazars and their Unification Schemes

2020 ◽  
Vol 29 (1) ◽  
pp. 168-178
Author(s):  
Evaristus U. Iyida ◽  
Finbarr C. Odo ◽  
Augustine E. Chukwude ◽  
Augustine A. Ubachukwu
Keyword(s):  
Selection Effect ◽  
Spectral Indices ◽  
Bl Lac Objects ◽  
X Ray ◽  
Spectrum Radio ◽  
Significant Difference ◽  
Evolutionary Connection ◽  
Galaxy Populations ◽  
The Relationship ◽  
Bl Lacs

AbstractWe use the distributions of spectral indices (αv ) of a large homogenous sample of Fermi-detected blazars to re-investigate the relationship between flat spectrum radio quasars (FSRQs) and subclasses of BL Lac objects (BL Lacs). We compute the broadband synchrotron and Compton spectral indices from radio-to-X-ray and X-ray to y-ray bands, respectively. Analyses of our data show continuity in the distributions of the spectral indices from FSRQs to HSP through LSP and ISP subclasses of BL Lacs. We find from y-ray luminosity distribution that the jetted radio galaxies form the low-luminosity tail of the distribution, which is suggestive that the sequence can be extended to the young jetted galaxy populations. We observe a significant difference in the shape of Compton and synchrotron spectra: significant anti-correlation (r ∼−0.80) exists between the broadband Compton and synchrotron spectral indices. Furthermore, the broadband spectral indices vary significantly with redshift (z) at low redshift (z < 0.3) and remain fairly constant at high (z ≥ 0.3) redshift. The trend of the variations suggests a form of evolutionary connection between subclasses of blazars. Thus, while selection effect may be significant at low redshift, evolutionary sequence can also be important. Our results are not only consistent with a unified scheme for blazars and their young jetted galaxy counterparts but also suggest that the broadband spectral sequence of blazars is not a secondary effect of redshift dependence.

scholarly journals Broadband X-ray observations of four gamma-ray narrow-line Seyfert 1 galaxies

2019 ◽  
Vol 632 ◽  
pp. A120 ◽  
Author(s):  
M. Berton ◽  
V. Braito ◽  
S. Mathur ◽  
L. Foschini ◽  
E. Piconcelli ◽  
...  
Keyword(s):  
Accretion Disk ◽  
Gamma Ray ◽  
High Energy ◽  
Time Variability ◽  
X Rays ◽  
Narrow Line ◽  
X Ray ◽  
Relativistic Jet ◽  
Line Region ◽  
Spectrum Radio

Narrow-line Seyfert 1 galaxies (NLS1s) is one of the few classes of active galactic nuclei harboring powerful relativistic jets and detected in γ-rays. NLS1s are well-known X-ray sources. While in non-jetted sources the origin of this X-ray emission may be a hot corona surrounding the accretion disk, in jetted objects, especially beamed ones, the contribution of corona and relativistic jet is difficult to disentangle without a proper sampling of the hard X-ray emission. For this reason, we observed with NuSTAR the first four NLS1s detected at high energy γ-rays. These data, along with XMM-Newton and Swift/XRT observations, confirmed that X-rays originate both in the jet and in the accretion disk corona. Time variability in hard X-rays furthermore suggests that, as observed in flat-spectrum radio quasars, the dissipation region during flares could change its position from source to source, and it can be located both inside and outside the broad-line region. We find that jetted NLS1s, and other blazars as well, seem not to follow the classical fundamental plane of black hole (BH) activity, which therefore should be used as a BH mass estimator in blazars with extreme care only. Our results strengthen the idea according to which γ-NLS1s are smaller and younger version of flat-spectrum radio quasars, in which both a Seyfert and a blazar component co-exist.

scholarly journals Radio VLBA polarization and multiband monitoring of the high-redshift quasar S5 0836 + 710 during a high-activity period

2019 ◽  
Vol 491 (1) ◽  
pp. 858-873 ◽  
Author(s):  
M Orienti ◽  
F D’Ammando ◽  
M Giroletti ◽  
D Dallacasa ◽  
G Giovannini ◽  
...  
Keyword(s):  
High Activity ◽  
Gamma Ray ◽  
High Redshift ◽  
Activity Period ◽  
X Rays ◽  
Large Area ◽  
The Core ◽  
Rotation Measure ◽  
Spectrum Radio ◽  
Γ Ray

ABSTRACT We report on results of a multiband monitoring campaign from radio to γ-rays of the high-redshift flat spectrum radio quasar S5 0836 + 710 during a high-activity period detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. Two major flares were detected, in 2015 August and November. In both episodes, the apparent isotropic γ-ray luminosity exceeds 1050 erg s−1, with a doubling time-scale of about 3 h. The high γ-ray activity may be related to a superluminal knot that emerged from the core in 2015 April at the peak of the radio activity and is moving downstream along the jet. The low variability observed in X-rays may indicate that X-ray emission is produced by the low-energy tail of the same electron population that produces the γ-ray emission. The analysis of full-polarization pc-scale radio observations suggests the presence of a limb-brightened polarization structure at about 1 mas from the core in which a rotation measure gradient with a sign change is observed transverse to the jet direction. These characteristics are consistent with a scenario in which Faraday rotation is produced by a sheath of thermal electrons with a toroidal magnetic field surrounding the emitting jet.

scholarly journals A new hard X-ray-selected sample of extreme high-energy peaked BL Lac objects and their TeV gamma-ray properties

2019 ◽  
Vol 486 (2) ◽  
pp. 1741-1762 ◽  
Author(s):  
L Foffano ◽  
E Prandini ◽  
A Franceschini ◽  
S Paiano
Keyword(s):  
Spectral Properties ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
High Energy ◽  
Spectral Energy ◽  
X Rays ◽  
Bl Lac Objects ◽  
X Ray ◽  
Bl Lac

ABSTRACT Extreme high-energy peaked BL Lac objects (EHBLs) are an emerging class of blazars with exceptional spectral properties. The non-thermal emission of the relativistic jet peaks in the spectral energy distribution (SED) plot with the synchrotron emission in X-rays and with the gamma-ray emission in the TeV range or above. These high photon energies may represent a challenge for the standard modelling of these sources. They are important for the implications on the indirect measurements of the extragalactic background light, the intergalactic magnetic field estimate, and the possible origin of extragalactic high-energy neutrinos. In this paper, we perform a comparative study of the multiwavelength spectra of 32 EHBL objects detected by the Swift-BAT telescope in the hard X-ray band and by the Fermi-LAT telescope in the high-energy gamma-ray band. The source sample presents uniform spectral properties in the broad-band SEDs, except for the TeV gamma-ray band where an interesting bimodality seems to emerge. This suggests that the EHBL class is not homogeneous, and a possible subclassification of the EHBLs may be unveiled. Furthermore, in order to increase the number of EHBLs and settle their statistics, we discuss the potential detectability of the 14 currently TeV gamma-ray undetected sources in our sample by the Cherenkov telescopes.

THE OPTICAL-X-RAY–GAMMA-RAY SPECTRAL ENERGY DISTRIBUTIONS OF GEV GAMMA-RAY LOUD BLAZARS AND CONNECTION AMONG LBLs, HBLs AND FSRQs

2003 ◽  
Vol 12 (05) ◽  
pp. 781-789 ◽  
Author(s):  
G. Z. XIE ◽  
S. X. DING ◽  
H. DAI ◽  
E. W. LIANG ◽  
H. T. LIU
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Spectral Energy ◽  
Spectral Indices ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
X Ray ◽  
Γ Ray ◽  
High Energy Emission ◽  
Bl Lacs

In this paper, we introduce a new composite spectral indices αγxγ = αxγ - αγ, and prove [Formula: see text], that means αγxγ is intrinsic. We plot a αxox - αγxγ diagram for 25 Gev γ-ray blazars for which αx and αγ have been provided in the literature, where αxox = αox - αx which was introduced by Sambruna et al. (1996) and proved that it is intrinsic by our previous paper (Xie et al. 2001). Using this new composite color–color (αxox - αγxγ) diagram, we investigated the nature of the HBLs–LBLs relationship, and the BL Lacs–FSRQs relationship, in high-energy emission. The results show that the spectral energy distributions of three subclasses of Gev γ-ray loud blazars are different, but essentially continuous: HBLs and FSRQs occupy separated regions while LBLs bridge the gap between HBLs and FSRQs. The results are consistent with that derived from a low energy color–color(αxox - αoro) diagram by Sambruna et al. (1996) and Xie et al. (2001). However, on the αox - αxγ diagram, FSRQs, LBLs and HBLs occupy same region. Because both αγxγ and αxox are intrinsic, thus, the new connection among HBLs, LBLs and FSRQs obtained by us is intrinsic.

scholarly journals The picture of relativistic jet from Fermi-LAT and multi-band observations of blazar 3C 279

2010 ◽  
Vol 6 (S275) ◽  
pp. 155-159
Author(s):  
Masaaki Hayashida ◽  
Greg Madejski
Keyword(s):  
Gamma Ray ◽  
First Year ◽  
Energy Bands ◽  
X Ray ◽  
Relativistic Jet ◽  
Spectrum Radio ◽  
Successful Launch ◽  
Γ Ray ◽  
Radio Quasar ◽  
Multi Band

AbstractStrong and variable radiation detected over all accessible energy bands in blazar arises from a relativistic, Doppler-boosted jet pointing close to our line of sight. Flat Spectrum Radio Quasar 3C 279 was one of the brightest γ-ray blazars in the sky at the time of the discovery with EGRET. Since the successful launch of the Fermi Gamma-ray Space telescope in 2008, we have organized extensive multi-band observational campaign of 3C 279 from radio to γ-ray bands, also including optical polarimetric observations. The uninterrupted monitoring in the γ-ray band by Fermi-LAT together with the multi-band data provide us with new insights of the relativistic jet of blazar. Here, we present the results of the first-year multi-band campaign of 3C 279 including the discovery of a γ-ray flare event associated with a dramatic change of the optical polarization - as well as a discovery of an “orphan” X-ray flare, unassociated with prominent outbursts in other bands.

scholarly journals OBSERVATIONAL EVIDENCES FOR SPINNING BLACK HOLES: A PROOF OF GENERAL RELATIVITY FOR SPACETIME AROUND ROTATING BLACK HOLES

2012 ◽  
Vol 21 (11) ◽  
pp. 1250086 ◽  
Author(s):  
BANIBRATA MUKHOPADHYAY ◽  
DEBBIJOY BHATTACHARYA ◽  
P. SREEKUMAR
Keyword(s):  
Black Holes ◽  
Gamma Ray ◽  
Kerr Metric ◽  
X Ray ◽  
Spin Parameter ◽  
Spectrum Radio ◽  
Γ Ray ◽  
X Ray Binaries ◽  
Bl Lacs ◽  
Adequate Data

Since it was theorized by Kerr in 1963, determining the spin of black holes from observed data was paid very little attention until few years back. The main reasons behind this were the unavailability of adequate data and the lack of appropriate techniques. In this paper, we explore determining/predicting the spin of several black holes in X-ray binaries (XRBs) and in the center of galaxies, using X-ray and gamma-ray satellite data. For X-ray binaries, in order to explain observed quasi-periodic oscillations (QPOs), our model predicts the spin parameter of underlying black holes. On the other hand, the nature of spin parameters of black holes in BL Lacs and flat spectrum radio quasars (FSRQs) is predicted by studying the total luminosities of systems based on Fermi γ-ray data. All sources considered here exhibit characteristics of spinning black holes, which verifies natural existence of the Kerr metric.

Studies of gamma-ray transitions in 146Eu

1976 ◽  
Vol 54 (2) ◽  
pp. 197-204 ◽  
Author(s):  
P. Sen ◽  
M. Kingman ◽  
H. Bakhru ◽  
N. Cue
Keyword(s):  
High Resolution ◽  
Level Scheme ◽  
Gamma Ray ◽  
X Rays ◽  
Accurate Evaluation ◽  
X Ray ◽  
Correlation Studies ◽  
Γ Rays ◽  
Γ Ray

The decay of 146Gd to levels of 146Eu has been studied using high resolution X-ray and γ-ray detectors. γ–γ directional correlation studies, using X and γ-ray Ge(Li) detectors, were made to assign the spins of the low lying states in 146Eu. γ–γ coincidence experiments with two Ge(Li) detectors and between Eu X rays and γ rays were performed to pin down the levels of 146Eu. On the basis of these measurements, Jπ of 4−, 3−, 2−, and 1− have been assigned respectively to the ground, 115.66, 230.51, and 385.11 keV states in 146Eu. More accurate evaluation of the E2 admixtures in the M1 transitions, 114.85, 115.66, and 154.60 keV, have been obtained. Based on the above results a tentative level scheme for 146Eu has been proposed.

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.

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