119234381
Suzaku X-ray spectral study of the Compton-thick Seyfert galaxy NGC 5135
We present the 0.5–50 keV Suzaku broad-band X-ray spectral study of the Compton-thick active galactic nucleus (AGN) in NGC 5135. The Suzaku observation provides the first detection of NGC 5135 above 10 keV that allowed us, for the first time, to estimate the absorbing column density, the intrinsic X-ray luminosity, the strength of the reflection component and the viewing angle of the torus for this AGN. The 0.5–10 keV spectrum of NGC 5135 is characterized by the standard components for a Compton-thick source: a scattered continuum, a prominent Fe Kα emission line [equivalent width (EW) ∼ 2.1 keV] and a soft excess. At higher energies (E > 10 keV), the intrinsic AGN continuum shows up, implying an absorbing column density of the order of ∼2.5 × 1024 cm−2 and the intrinsic 2.0–10 keV X-ray luminosity of ∼1.8 × 1043 erg s−1. Assuming a toroidal geometry of the reprocessing material, we show that an edge-on view of the obscuring torus is preferred in this source.
54620466
Measuring the level of nuclear activity in Seyfert galaxies and the unification scheme
Context. The unification scheme of Seyfert galaxies hypothesizes that Seyfert type 1s and type 2s are intrinsically similar and the observed differences between the two subtypes are solely due to the differing orientations of toroidal-shaped obscuring material around the AGN. In the framework of the unification scheme, both the Seyfert subtypes are expected to show similar intrinsic nuclear properties such as the absorption-corrected AGN X-ray luminosity, bolometric luminosity, accretion rate and the mass of the supermassive black hole. Aims. To test the predictions of the Seyfert unification scheme, we make statistical comparison of the distributions of: (i) the absorption-corrected 2.0‐10 keV X-ray luminosities; (ii) the bolometric luminosities; (iii) the black hole masses and; (iv) the Eddington ratios, of Seyfert type 1s and type 2s. Methods. We use an optically selected Seyfert sample in which type 1s and type 2s are matched in properties that are independent to the orientation of the obscuring torus, the AGN axis and the host galaxy. Results. The distributions of the absorption-corrected 2.0‐10 keV X-ray luminosities (L c.0−10 keV ), the bolometric luminosities (LBol), the black masses (MBH) and, the Eddington ratios (λ) are statistically similar for the two Seyfert subtypes, consistent with the orientation and obscuration based Seyfert unification scheme. The Eddington ratio distributions suggest that both the Seyfert subtypes are accreting at sub-Eddington level with wide span of Eddington ratios i.e., 10 −4 ‐10 −1 .
118486527
X-ray spectral properties of Seyfert galaxies and the unification scheme
Context. The unification scheme of Seyfert galaxies predicts that the observed differences between types 1 and 2 Seyfert galaxies are solely due to the differing orientations of the toroidal-shaped obscuring material around AGN. The observed X-ray spectra of Seyfert type 2s compared to type 1s are expected to be affected by higher absorbing column density owing to the edge-on view of the obscuring torus. Aims. We study the 0.5‐10 keV X-ray spectral properties of Seyfert type 1s and type 2s with the aim of testing the predictions of Seyfert unification scheme in the X-ray regime. Methods. We use an optically selected Seyfert sample in which type 1s and type 2s have matched distributions in parameters that are independent of the orientation of AGN and the host galaxy. Results. The 0.5‐10 keV XMM-Newton pn X-ray spectra of Seyfert galaxies are in general best fitted with a model that consists of (i) an absorbed powerlaw; (ii) a narrow Gaussian fitted to the Fe Kα emission line; and (iii) an often seen soft-excess component characterized by either a thermal plasma model with temperature kT ∼ 0.1‐1.0 keV or a steep powerlaw or both. The 2.0‐10 keV hard X-ray continuum emission in several Seyfert type 2s is dominated by reflection and suggests the Compton-thick obscuration. Results of the statistical comparison between the distributions of (i) the observed X-ray luminosities in the soft (0.5‐2.0 keV) and hard (2.0‐10.0 keV) bands; (ii) the X-ray absorbing column densities; (iii) the equivalent widths of Fe Kα line; and (iv) the flux ratios of hard X-ray to [OIII] λ5007 A, for the two Seyfert subtypes are consistent with the obscuration and orientation-based unification scheme.
119287764
Low-frequency radio observations of Seyfert galaxies: A test of the unification scheme
Aims. We present low-frequency radio imaging and spectral properties of a well defined sample of Seyfert galaxies using GMRT 240/610 MHz dual frequency observations. Radio spectra of Seyfert galaxies over 240 MHz to 5.0 GHz are investigated using 240 MHz, 610 MHz flux densities derived from GMRT, and 1.4 GHz and 5.0 GHz flux densities mainly from published VLA data. We test the predictions of Seyfert unification scheme by comparing the radio properties of Seyfert type 1s and type 2s. Methods. We choose a sample such that the two Seyfert subtypes have matched distributions in parameters that are independent to the orientation of AGN, obscuring torus and the host galaxy. Our sample selection criteria allow us to assume that the two Seyfert subtypes are intrinsically similar within the framework of the unification scheme. Results. The new observations at 240/610 MHz, together with archival observations at 1.4 GHz, 5.0 GHz show that type 1s and type 2s have statistically similar radio luminosity distributions at 240 MHz, 610 MHz, 1.4 GHz and 5.0 GHz. The spectral indices at selected frequency intervals as well as index measured over 240 MHz to 5.0 GHz for the two Seyfert subtypes have similar distributions with median spectral index $/sim$ -0.7, consistent with the synchrotron emission from optically thin plasma. In our snap-shot 240/610 MHz GMRT observations, most of the Seyfert galaxies show primarily an unresolved central radio component, except a few sources in which faint kpc-scale extended emission is apparent at 610 MHz. Our results on the statistical comparison of the multifrequency radio properties of our sample Seyfert galaxies are in agreement with the predictions of the Seyfert unification scheme.
121164064
The "Herbst Hamiltonian" and the mass of boson stars
Abstract We present new accurate lower bounds on the ground state of the Hamiltonian p 2 +m 2 − α r . From these, we obtain a lower bound on the maximum mass of a boson star in the semirelativistic framework, and we compare it to a variational upper bound. We get 0.846 ( Gm ) −1 M max Gm ) −1 , where G is Newton's constant and m the boson mass.
119107308
Hadron spectra in p+p collisions at RHIC and LHC energies
We present the systematic analysis of transverse momentum (pT) spectra of identified hadrons in p+p collisions at Relativistic Heavy Ion Collider ( and 200 GeV) and at Large Hadron Collider (LHC) energies (, 2.76 and 7.0 TeV) using phenomenological fit functions. We review various forms of Hagedorn and Tsallis distributions and show their equivalence. We use Tsallis distribution which successfully describes the spectra in p+p collisions using two parameters, Tsallis temperature T which governs the soft bulk spectra and power n which determines the initial production in partonic collisions. We obtain these parameters for pions, kaons and protons as a function of center-of-mass energy . It is found that the parameter T has a weak but decreasing trend with increasing . The parameter n decreases with increasing which shows that production of hadrons at higher energies are increasingly dominated by point like qq scatterings. Another important observation is with increasing , the separation between the powers for protons and pions narrows down hinting that the baryons and mesons are governed by same production process as one moves to the highest LHC energy.
122369339
Electron identification and the detection of synchrotron radiation with a preshower detector
Abstract Results are presented from testbeam measurements made with a scintillating fiber preshower detector. The detector was designed to study the early development of electromagnetic showers and the conversion of synchrotron radiation photons. It was constructed with a 0.5 mm transverse granularity, and eight 0.25 radiation length ( X 0 ) longitudinal samplings. Data were taken with 50 GeV pions and electrons with energies between 10 and 200 GeV. Measurements, for electrons, of both the energy deposited and the shower width as a function of depth are presented in this paper. In addition, data were taken with a 1.8 m long magnet with a 2.5 T field placed directly upstream of the detector and the synchrotron radiation photons, generated by the electrons traversing it, were observed in our detector. Electron identification efficiencies and pion rejection factors based on the synchrotron radiation signal and the energy deposited in the last sampling layer (1.75 X 0 ) are presented.
119470470
Measurement of semi electronic decay of heavy flavor mesons in d+Au collision at RHIC using PHENIX detector
Abstract The PHENIX detector at RHIC has measured single electron spectra from heavy flavor decays in p+p and Au+Au collisions at s N N = 200 GeV . A strong suppression is observed compared to the binary scaling of p+p collisions for high p T single electrons in Au+Au collisions providing evidence for strong medium effects. The motivation for measuring the single electron spectra from the decay of heavy flavor mesons in d+Au collisions from the 2008 RHIC run (Run8) is to determine parton distribution modifications, the Cronin effect and possible energy loss present in cold nuclear matter. These phenomena can mask hot nuclear matter effects and therefore must be understood in order to interpret the Au+Au results. The analysis is still in progress, but the latest results and technical details are being shown in the current paper.
119188201
Emission characteristics of the projectile fragments at relativistic energy
A projectile (84Kr36) having kinetic energy around 1 A GeV has been used to expose NIKFI BR-2 emulsion target at GSI, Darmstadt, Germany. A total of 700 inelastic events has been identified and used in the present studies on projectile fragments. The emission angle of the projectile fragments are strongly affected by charge of the other projectile fragments emitted at same time with different emission angle is observed. The angular distribution studies show symmetrical nature for lighter charge projectile fragments. The symmetrical nature decreased with the charge of projectile fragments. We have observed at ~4o of emission angle for double charge projectile fragments, the momentum transfer during interaction is similar for various target species of emulsion. We have also observed a small but significant amplitude peaks on both side of the big peak for almost all light charge projectile fragments having different delta angle values. It reflects that there are a few percent of projectile fragments that are coming from the decay of heavy projectile fragments or any other process.