Results for "Aneta Siemiginowska"

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X-ray emission from GPS and CSS sourcesJan 09 2009Many X-ray observations of GigaHertz Peaked Spectrum and Compact Steep Spectrum sources have been made with Chandra X-ray Observatory and XMM-Newton Observatory over the last few years. The X-ray spectra contribute the important information to the total ... More
Models of Accretion DisksMar 06 2012An accretion flow onto a supermassive black hole is the primary process powering quasars. However, a geometry of this flow is not well constrained. Both global MHD simulations and observations suggest that there are several emission components present ... More
The Impact of the Environment on the Early Stages of Radio Source EvolutionDec 05 2018Compact Symmetric Objects (CSOs) show radio features such as jets, lobes, hot spots that are contained within the central 1 kpc region of their host galaxy. Thus, they are thought to be among the progenitors of large-scale radio galaxies. A debate on ... More
Deriving the Quasar Luminosity Function from Accretion Disk InstabilitiesMar 14 1997We have derived the quasar luminosity function assuming that the quasar activity is driven by a thermal-viscous unstable accretion disk around a supermassive black hole. The instabilities produce large amplitude, long-term variability of a single source. ... More
Evidence for a TDE origin of the radio transient Cygnus A-2Apr 12 2019In 2015, a radio transient named Cygnus A-2 was discovered in Cygnus A with the Very Large Array. Because of its radio brightness ($\nu F_{\nu} \approx 6 \times 10^{39}$ erg s$^{-1}$), this transient likely represents a secondary black hole in orbit around ... More
The 300 kpc Long X-ray Jet in PKS 1127-145, z=1.18 Quasar: Constraining X-ray Emission ModelsNov 14 2006We present a ~100 ksec Chandra X-ray observation and new VLA radio data of the large scale, 300 kpc long X-ray jet in PKS1127-145, a radio loud quasar at redshift z=1.18. With this deep X-ray observation we now clearly discern the complex X-ray jet morphology ... More
Sherpa: a Mission-Independent Data Analysis ApplicationAug 27 2001The ever-increasing quality and complexity of astronomical data underscores the need for new and powerful data analysis applications. This need has led to the development of Sherpa, a modeling and fitting program in the CIAO software package that enables ... More
Are the Variations in Quasar Optical Flux Driven by Thermal Fluctuations?Mar 30 2009We analyze a sample of optical light curves for 100 quasars, 70 of which have black hole mass estimates. Our sample is the largest and broadest used yet for modeling quasar variability. The sources in our sample have z < 2.8 and 10^6 < M_BH < 10^10. We ... More
Radiation pressure instability driven variability in the accreting black holesMay 15 2002The time dependent evolution of the accretion disk around black hole is computed. The classical description of the $\alpha$-viscosity is adopted so the evolution is driven by the instability operating in the innermost radiation-pressure dominated part ... More
A Stochastic Model for the Luminosity Fluctuations of Accreting Black HolesSep 29 2010Feb 02 2011In this work we have developed a new stochastic model for the fluctuations in lightcurves of accreting black holes. The model is based on a linear combination of stochastic processes and is also the solution to the linear diffusion equation perturbed ... More
Radiation pressure instability as a variability mechanism in the microquasar GRS 1915+105Aug 23 2000Physical mechanism responsible for high viscosity in accretion disks is still under debate. Parameterization of the viscous stress as $\alpha P$ proved to be a successful representation of this mechanism in the outer parts of the disk, explaining the ... More
Chandra Observations of the QSO Pair Q2345+007: Binary Quasar or Massive Dark Lens?Feb 04 2002The components of the wide (7.3") separation quasar pair Q2345+007A,B (z=2.15) have the most strikingly similar optical spectra seen to date (Steidel & Sargent 1991) yet no detected lensing mass, making this system the best candidate known for a massive ... More
COMP2CAT: hunting compact double radio sources in the local UniverseMay 06 2019We present a catalog of compact double radio galaxies (hereafter COMP2$CAT$) listing 43 edge-brightened radio sources whose projected linear size does not exceed 60 kpc, the typical size of their host galaxies. This is the fifth in a series of radio source ... More
Searching for Narrow Emission Lines in X-ray Spectra: Computation and MethodsAug 23 2008The detection and quantification of narrow emission lines in X-ray spectra is a challenging statistical task. The Poisson nature of the photon counts leads to local random fluctuations in the observed spectrum that often results in excess emission in ... More
Origin of the complex radio structure in BAL QSO 1045+352Jul 08 2010We present new more sensitive high-resolution radio observations of a compact broad absorption line (BAL) quasar, 1045+352, made with the EVN+MERLIN at 5 GHz. They allowed us to trace the connection between the arcsecond structure and the radio core of ... More
Accretion of Low Angular Momentum Material onto Black Holes: Radiation Properties of Axisymmetric MHD FlowsJul 10 2007Numerical simulations of MHD accretion flows in the vicinity of a supermasssive black hole provide important insights to the problem of why and how systems -- such as the Galactic Center -- are underluminous and variable. To access applicability of such ... More
X-Ray Emission from the Quasar PKS 1127-145: Comptonized IR Photons on Parsec ScalesNov 17 2003We model the broad-band spectral energy distribution of the innermost "core-jet" region of the redshift z=1.187 quasar PKS 1127-145. We propose a scenario where the high energy photons are produced via the Compton scattering of thermal IR radiation by ... More
Probing the accretion disk - jet connection via instabilities in the inner accretion flow. From microquasars to quasarsOct 05 2010We present various instability mechanisms in the accreting black hole systems which might indicate at the connection between the accretion disk and jet. The jets observed in microquasars can have a persistent or blobby morphology. Correlated with the ... More
Variability Model for the Microquasar GRS 1915+105Apr 25 2000We analyse the radiation pressure instability of the standard, optically thisc disc and propose it as an explanation of the obseved variability of the superluminal microquasar GRS 1915+105. The quantitave agreement with the observed outburst amplitudes ... More
Detecting Relativistic X-ray Jets in High-Redshift QuasarsSep 12 2016We analyze Chandra X-ray images of a sample of 11 quasars that are known to contain kiloparsec scale radio jets. The sample consists of five high-redshift (z >= 3.6) flat-spectrum radio quasars, and six intermediate redshift (2.1 < z < 2.9) quasars. The ... More
Stochastic Modeling of the Fermi/LAT Gamma-ray Blazar VariabilityMar 20 2014We study the gamma-ray variability of 13 blazars observed with the Fermi Large Area Telescope (LAT). These blazars have the most complete light curves collected during the first 4 years of the Fermi sky survey. We model them with the Ornstein-Uhlenbeck ... More
Constraints on AGN accretion disc viscosity derived from continuum variabilitySep 10 2003We estimate a value of the viscosity parameter in AGN accretion discs for the PG quasar sample. We assume that optical variability on time-scales of months to years is caused by local instabilities in the inner accretion disc. Comparing the observed variability ... More
On the turbulent $α$-disks and the intermittent activity in AGNNov 01 2003We consider effects of the MHD turbulence on the viscosity during the evolution of the thermal-viscous ionization instability in the standard $\alpha$-accretion disks. We consider the possibility that the accretion onto a supermassive black hole proceeds ... More
Accounting for Calibration Uncertainties in X-ray Analysis: Effective Areas in Spectral FittingFeb 22 2011While considerable advance has been made to account for statistical uncertainties in astronomical analyses, systematic instrumental uncertainties have been generally ignored. This can be crucial to a proper interpretation of analysis results because instrumental ... More
Observational Constraints on the Dependence of Radio-Quiet Quasar X-ray Emission on Black Hole Mass and Accretion RateJan 15 2008In this work we use a sample of 318 radio-quiet quasars (RQQ) to investigate the dependence of the ratio of optical/UV flux to X-ray flux, alpha_ox, and the X-ray photon index, Gamma_X, on black hole mass, UV luminosity relative to Eddington, and X-ray ... More
X-ray emission from GPS/CSS sourcesJun 13 2003The high spatial resolution of the Chandra X-ray Observatory allows us to study the environment of GPS/CSS sources to within an arcsec of the strong compact core. We present the discovery of X-ray jets in two GPS quasars, PKS1127-145 and B2 0738+393, ... More
Correlation between X-ray and radio absorption in compact radio galaxiesSep 25 2017Oct 30 2017Compact radio galaxies with a GHz-peaked spectrum (GPS) and/or compact-symmetric-object (CSO) morphology (GPS/CSOs) are increasingly detected in the X-ray domain. Their radio and X-ray emissions are affected by significant absorption. However, the locations ... More
Intermittent Activity of Jets in AGNFeb 27 2010Large scale X-ray jets that extend to >100 kpc distances from the host galaxy indicate the importance of jets interactions with the environment on many different physical scales. Morphology of X-ray clusters indicate that the radio-jet activity of a cD ... More
X-ray Properties of the GigaHertz-Peaked and Compact Steep Spectrum SourcesApr 09 2008We present {\it Chandra} X-ray Observatory observations of Giga-Hertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radio sources. The {\it Chandra} sample contains 13 quasars and 3 galaxies with measured 2-10 keV X-ray luminosity within $10^{42} ... More
Analysis of Energy Spectra with Low Photon Counts via Bayesian Posterior SimulationAug 11 2000Over the past 10 years Bayesian methods have rapidly grown more popular as several computationally intensive statistical algorithms have become feasible with increased computer power. In this paper, we begin with a general description of the Bayesian ... More
Submillimeter Variability and the Gamma-ray Connection in Fermi BlazarsJan 06 2010We present multi-epoch observations from the Submillimeter Array (SMA) for a sample of 171 bright blazars, 43 of which were detected by Fermi during the first three months of observations. We explore the correlation between their gamma-ray properties ... More
Chandra Detection of X-ray Absorption Associated with a Damped Lyman Alpha SystemJun 30 2001We have observed three quasars, PKS 1127-145, Q 1331+171 and Q0054+144, with the ACIS-S aboard the Chandra X-ray Observatory, in order to measure soft X-ray absorption associated with intervening 21-cm and damped Ly$\alpha$ absorbers. For PKS 1127-145, ... More
150 keV Emission from PKS2149-306 with BeppoSAXJun 16 2000Jul 24 2001A BeppoSAX observation of the z=2.34 quasar PKS2149-306 produced a strong signal in the high energy PDS instrument up to a maximum observed energy of nearly 50 keV, 150 keV in the quasar frame. The Beppo-SAX spectrum spans almost 3 decades (0.3-150 keV, ... More
Strong Lens Time Delay Challenge: II. Results of TDC1Sep 03 2014Dec 12 2014We present the results of the first strong lens time delay challenge. The motivation, experimental design, and entry level challenge are described in a companion paper. This paper presents the main challenge, TDC1, which consisted of analyzing thousands ... More
Bayesian Estimates of Astronomical Time Delays between Gravitationally Lensed Stochastic Light CurvesFeb 03 2016The gravitational field of a galaxy can act as a lens and deflect the light emitted by a more distant object such as a quasar. If the galaxy is a strong gravitational lens, it can produce multiple images of the same quasar in the sky. Since the light ... More
Detecting Unspecified Structure in Low-Count ImagesOct 15 2015Unexpected structure in images of astronomical sources often presents itself upon visual inspection of the image, but such apparent structure may either correspond to true features in the source or be due to noise in the data. This paper presents a method ... More
An X-ray jet discovered by Chandra in the z=4.3 radio-selected quasar GB 1508+5714Oct 09 2003We report the Chandra discovery of an X-ray jet associated with the redshift 4.3 radio-loud quasar GB 1508+5714. The jet X-ray emission peaks ~2 arcsec to the South-West of the quasar core. We present archival HST WFPC2 data of the quasar field which ... More
Chandra Discovery of a 300 kpc X-ray Jet in the GPS Quasar PKS1127-145Jan 08 2002We have discovered an X-ray jet with Chandra imaging of the z=1.187 radio-loud quasar PKS1127-145. In this paper we present the Chandra X-ray data, follow-up VLA observations, and optical imaging using the HST WFPC2. The X-ray jet contains 273+/-5 net ... More
Accretion Disk Model of Short-Timescale Intermittent Activity in Young Radio SourcesMar 23 2009We associate the existence of short-lived compact radio sources with the intermittent activity of the central engine caused by a radiation pressure instability within an accretion disk. Such objects may constitute a numerous sub-class of Giga-Hertz Peaked ... More
Flexible and Scalable Methods for Quantifying Stochastic Variability in the Era of Massive Time-Domain Astronomical Data SetsFeb 24 2014May 07 2014We present the use of continuous-time autoregressive moving average (CARMA) models as a method for estimating the variability features of a light curve, and in particular its power spectral density (PSD). CARMA models fully account for irregular sampling ... More
Equilibrium and stability of relativistic stars in extended theories of gravityApr 14 2016Jul 29 2016We study static, spherically symmetric equilibrium configurations in extended theories of gravity (ETG) following the notation introduced by Capozziello et {\it al}. We calculate the differential equations for the stellar structure in such theories in ... More
Statistics: Handle with Care, Detecting Multiple Model Components with the Likelihood Ratio TestJan 31 2002The likelihood ratio test (LRT) and the related $F$ test, do not (even asymptotically) adhere to their nominal $\chi^2$ and $F$ distributions in many statistical tests common in astrophysics, thereby casting many marginal line or source detections and ... More
Q1208+1011: Search for the lensing galaxyMar 13 1998We present a high-resolution spectrum of the high redshift, lensed quasar Q1208+1101, obtained with the echellette spectrograph on the Multiple Mirror Telescope. We examine the new and published spectra and provide an updated list of high-confidence metal-line ... More
Evolution of the X-ray Emission of Radio-Quiet QuasarsNov 03 2006We report new Chandra observations of seven optically faint, z \sim 4 radio-quiet quasars. We have combined these new observations with previous Chandra observations of radio-quiet quasars to create a sample of 174 sources. These sources have 0.1 < z ... More
Bayesian Estimates of Astronomical Time Delays between Gravitationally Lensed Stochastic Light CurvesFeb 03 2016Jan 30 2017The gravitational field of a galaxy can act as a lens and deflect the light emitted by a more distant object such as a quasar. Strong gravitational lensing causes multiple images of the same quasar to appear in the sky. Since the light in each gravitationally ... More
Compactly Supported Cohomology Groups of Toric SurfacesMay 23 2015This article uses homological methods for evaluating compactly supported cohomology groups of noncompact toric surfaces
Constraints on Black Hole Growth, Quasar Lifetimes, and Eddington Ratio Distributions from the SDSS Broad Line Quasar Black Hole Mass FunctionJun 17 2010We present an estimate of the black hole mass function (BHMF) of broad line quasars (BLQSOs) that self-consistently corrects for incompleteness and the statistical uncertainty in the mass estimates, based on a sample of 9886 quasars at 1 < z < 4.5 drawn ... More
The X-ray absorber of PKS2126-158Jun 25 2003Jun 26 2003BeppoSAX observed the z=3.27 quasar PKS2126-158 on 1999 May 24-28 when its 2-10keV and 0.1-2.5keV fluxes were 1.1E-11 and 4.4E-12 cgs respectively, a factor of 2 higher than in all previous ROSAT and ASCA observations and 40% higher than in two more recent ... More
First detection in gamma-rays of a young radio galaxy: Fermi-LAT observations of the Compact Symmetric Object PKS 1718-649Apr 07 2016We report the $\gamma$-ray detection of a young radio galaxy, PKS 1718$-$649, belonging to the class of Compact Symmetric Objects (CSOs), with the Large Area Telescope (LAT) on board the {\it Fermi} satellite. The third {\it Fermi} Gamma-ray LAT catalog ... More
Jet Emission in Young Radio Sources: a Fermi-LAT Gamma-ray ViewNov 29 2013We 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 gamma-ray band. We derive predictions on the gamma-ray luminosities associated ... More
Nuclear X-ray properties of the peculiar radio-loud hidden AGN 4C+29.30Aug 22 2012We present results from a study of a nuclear emission of a nearby radio galaxy, 4C+29.30, over a broad 0.5-200 keV X-ray band. This study used new XMM-Newton (~17 ksec) and Chandra (~300 ksec) data, and archival Swift/BAT data from the 58-month catalog. ... More
X-ray properties of the Youngest Radio Sources and their EnvironmentsMar 03 2016Apr 14 2016We present the results of the first X-ray study of a sample of 16 young radio sources classified as Compact Symmetric Objects (CSOs). We observed six of them for the first time in X-rays using {\it Chandra}, re-observed four with the previous {\it XMM-Newton} ... More
Using the Additive Property of Compactly Supported Cohomology GroupsSep 05 2012This article uses basic homological methods for evaluating examples of compactly supported cohomology groups of line bundles over projective curve.
The long-term behavior of number of near-maximum insurance claimsApr 05 2019A near-maximum insurance claim is one falling within a distance $a$ of the current maximal claim. In this paper, we investigate asymptotic behavior of normalized numbers of near-maximum insurance claims under the assumption that the sequence of successive ... More
Groupoids and inverse semigroups associated to W*-algebrasOct 28 2011Feb 01 2012We investigate the Banach Lie groupoids and inverse semigroups naturally associated to W*-algebras. We also present statements describing relationship between these groupoids and the Banach Poisson geometry which follows in the canonical way from the ... More
Bayesian Estimation of Hardness Ratios: Modeling and ComputationsJun 10 2006A commonly used measure to summarize the nature of a photon spectrum is the so-called Hardness Ratio, which compares the number of counts observed in different passbands. The hardness ratio is especially useful to distinguish between and categorize weak ... More
High redshift X-ray cooling-core cluster associated with the luminous radio loud quasar 3C186Aug 10 2010Aug 11 2010We present the first results from a new, deep (200ks) Chandra observation of the X-ray luminous galaxy cluster surrounding the powerful (L ~10^47 erg/s), high-redshift (z=1.067), compact-steep-spectrum radio-loud quasar 3C186. The diffuse X-ray emission ... More
X-ray Cluster Associated with the z=1.063 CSS Quasar 3C 186: The Jet is NOT FrustratedJun 16 2005We report the Chandra discovery of an X-ray cluster at redshift z = 1.063 associated with the Compact Steep Spectrum radio loud quasar 3C 186 (Q0740+380). Diffuse X-ray emission is detected out to ~120 kpc from the quasar and contains 741+/-40 net counts. ... More
Relativistic X-ray jets at high redshiftDec 31 2018Powerful radio sources and quasars emit relativistic jets of plasma and magnetic fields that travel hundreds of kilo-parsecs, ultimately depositing energy into the intra- or inter-cluster medium. In the rest frame of the jet, the energy density of the ... More
Accretion and nuclear activity of quiescent supermassive black holes. II: optical study and interpretationNov 11 2005Our X-ray study of the nuclear activity in a new sample of six quiescent early-type galaxies, and in a larger sample from the literature, confirmed (Soria et al., Paper I) that the Bondi accretion rate of diffuse hot gas is not a good indicator of the ... More
Accretion and nuclear activity of quiescent supermassive black holes. I: X-ray studyNov 10 2005We have studied the nuclear activity in a sample of six quiescent early-type galaxies, with new Chandra data and archival HST optical images. Their nuclear sources have X-ray luminosities ~ 10^{38} - 10^{39} erg/s (L_X/L_Edd ~ 10^{-8} - 10^{-7}), and ... More
The Case of the 300 kpc Long X-ray Jet in PKS 1127-145 at z=1.18Aug 09 2007The complex X-ray morphology of the 300 kpc long X-ray jet in PKS1127-145 (z=1.18 quasar) is clearly discerned in a ~100 ksec Chandra observation. The jet X-ray surface brightness gradually decreases by an order of magnitude going out from the core. The ... More
Evolution of a Powerful Radio Loud Quasar 3C186 and its Impact on the Cluster Environment at z=1Aug 09 2007X-ray cluster emission has been observed mainly in clusters with "inactive" cD galaxies (L_bol ~1E40-1E43erg/sec), which do not show signs of accretion onto a SMBH. Our recent Chandra discovery of ~100kpc scale diffuse X-ray emission revealed the presence ... More
Chandra Survey of Radio-quiet, High-redshift QuasarsApr 26 2002We observed 17 optically-selected, radio-quiet high-redshift quasars with the Chandra Observatory ACIS, and detected 16 of them. The quasars have redshift between 3.70 and 6.28 and include the highest redshift quasars known. When compared to low-redshift ... More
Unsteady flows of heat-conducting non-Newtonian fluids in~Musielak-Orlicz spacesNov 16 2015Our purpose is to show the existence of weak solutions for unsteady flow of non-Newtonian incompressible nonhomogeneous, heat-conducting fluids with generalised form of the stress tensor without any restriction on its upper growth. Motivated by fluids ... More
On Computing Upper Limits to Source IntensitiesJun 22 2010A common problem in astrophysics is determining how bright a source could be and still not be detected. Despite the simplicity with which the problem can be stated, the solution involves complex statistical issues that require careful analysis. In contrast ... More
Accretion Disk Instabilities, CDM models and their role in Quasar EvolutionSep 07 2000We have developed a consistent analytical model to describe the observed evolution of the quasar luminosity function. Our model combines black hole mass distributions based on the Press - Schechter theory of the structure formation in the Universe with ... More
Simulated spectral states of AGN and observational predictionsFeb 03 2011Active galactic nuclei (AGN) and galactic black hole binaries (GBHs) represent two classes of accreting black holes. They both contain an accretion disc emitting a thermal radiation, and a non-thermal X-ray emitting corona. GBHs exhibit state transitions, ... More
The incompressible limit of compressible finitely extensible nonlinear bead-spring chain models for dilute polymeric fluidsJun 11 2019We explore the behaviour of global-in-time weak solutions to a class of bead-spring chain models, with finitely extensible nonlinear elastic (FENE) spring potentials, for dilute polymeric fluids. In the models under consideration the solvent is assumed ... More
An X-ray cooling-core cluster surrounding a low power Compact Steep Spectrum Radio source 1321+045Jun 24 2013We discovered an X-ray cluster in a Chandra observation of the compact steep spectrum (CSS) radio source 1321+045 (z=0.263). CSS sources are thought to be young radio objects at the beginning of their evolution and can potentially test the cluster heating ... More
Optical Detection of the Pictor A Jet and Tidal Tail: Evidence against an IC/CMB jetJun 15 2015New images from the Hubble Space Telescope of the FRII radio galaxy Pictor A reveal a previously undiscovered tidal tail, as well as a number of jet knots coinciding with a known X-ray and radio jet. The tidal tail is approximately 5" wide (3 kpc projected), ... More
Design of engineering systems in Polish mines in the third quarter of the 20th centuryMar 30 2018Participation of mathematicians in the implementation of economic projects in Poland, in which mathematics-based methods played an important role, happened sporadically in the past. Usually methods known from publications and verified were adapted to ... More
A family of integrable perturbed Kepler systemsJan 13 2019Jan 18 2019In the framework of the Poisson geometry of twistor space we consider a family of perturbed 3-dimensional Kepler systems. We show that Hamilton equations of this systems are integrated by quadratures. Their solutions for some subcases are given explicitly ... More
Broad-band Jet Emission in Young and Powerful Radio Sources: the Case of the CSS Quasar 3C 186Feb 14 2012We present the X-ray analysis of a deep ~200 ksec Chandra observation of the compact steep spectrum radio-loud quasar 3C 186 (z=1.06) and investigate the contribution of the unresolved radio jet to the total X-ray emission. The spectral analysis is not ... More
Quasi-random Agents for Image Transition and AnimationOct 20 2017Quasi-random walks show similar features as standard random walks, but with much less randomness. We utilize this established model from discrete mathematics and show how agents carrying out quasi-random walks can be used for image transition and animation. ... More
Evolution of Images with Diversity and Constraints Using a Generator NetworkFeb 15 2018Evolutionary search has been extensively used to generate artistic images. Raw images have high dimensionality which makes a direct search for an image challenging. In previous work this problem has been addressed by using compact symbolic encodings or ... More
Evolutionary Image Transition Based on Theoretical Insights of Random ProcessesApr 21 2016Evolutionary algorithms have been widely studied from a theoretical perspective. In particular, the area of runtime analysis has contributed significantly to a theoretical understanding and provided insights into the working behaviour of these algorithms. ... More
On the existence of static spherically-symmetric objects in action-dependent Lagrangian theoriesMar 28 2019We study static symmetric solutions in the context of a gravitational theory based on a action-dependent Lagrangian. Such theory has been designed as a setup to implement dissipative effects into the traditional principle of least action. Dissipation ... More
Confronting X-ray Emission Models with the Highest-Redshift Kiloparsec-scale Jets: the z=3.89 Jet in Quasar 1745+624Jun 12 2006Jun 12 2006A newly identified kiloparsec-scale X-ray jet in the high-redshift z=3.89 quasar 1745+624 is studied with multi-frequency Very Large Array, Hubble Space Telescope, and Chandra X-ray imaging data. This is only the third large-scale X-ray jet beyond z>3 ... More
Chandra Discovery of an X-ray jet and Extended X-ray Structure in z=0.63 quasar, B2 0738+313Jun 05 2003We have made a 30 ksec Chandra observation of the redshift z=0.63 GPS quasar B2 0738+313. We detected X-ray emission from the core and have discovered a 200 kpc (projected on the sky) X-ray jet. The X-ray jet is narrow and curves, following the extended ... More
What can we learn about quasars from alpha_OX measurements in galactic black hole binaries?Jan 15 2009We draw a comparison between AGN and Galactic black hole binaries using a uniform description of spectral energy distribution of these two classes of accreting X-ray sources. We parametrize spectra of GBHs with an alpha_GBH parameter which we define as ... More
Algebroids associated to the groupoid of partially invertible elements of a $W^*$-algebraJan 04 2014In the paper we study the algebroid A of the groupoid of partially invertible elements over the lattice of orthogonal projections of a $W^*$-algebra. In particular the complex analytic manifold structure of these objects is investigated. The expressions ... More
Deep Chandra X-ray Imaging of a Nearby Radio Galaxy 4C+29.30: X-ray/Radio ConnectionMar 06 2012We report results from our deep Chandra X-ray observations of a nearby radio galaxy, 4C+29.30 (z=0.0647). The Chandra image resolves structures on sub-arcsec to arcsec scales, revealing complex X-ray morphology and detecting the main radio features: the ... More
Galaxy Rotation Curves via Conformal FactorsMay 11 2017Apr 11 2018We propose a new formula to explain circular velocity profiles of spiral galaxies obtained from the Starobinsky model in Palatini formalism. It is based on the assumption that the gravity can be described by two conformally related metrics: one of them ... More
Efficient distribution and improved security for reliable cloud storage systemFeb 05 2016The distributed data storage systems are constructed by large number of nodes which are interconnected over a network. Each node in such peer-to-peer network is vulnerable and at a potential risk for attack. The attackers can eavesdrop the nodes and possibly ... More
Symmetries of the space of connections on a principal G-bundle and related symplectic structuresDec 22 2017We investigate G-invariant symplectic structures on the cotangent bundle T*P of a principal G-bundle P(M,G) which are canonically related to automorphisms of the tangent bundle TP covering the identity map of P and commuting with the action of TG on TP. ... More
Poisson Geometry Related to Atiyah SequencesJun 10 2015Jan 10 2018We construct and investigate a short exact sequence of Poisson $\mathcal{VB}$-groupoids which is canonically related to the Atiyah sequence of a $G$-principal bundle $P$. Our results include a description of the structure of the symplectic leaves of the ... More
Poisson geometry related to Atiyah sequencesJun 10 2015We construct and investigate a short exact sequence of Poisson VB-groupoids which is canonically related to the Atiyah sequence of a G-principal bundle P. Our results include a description of the structure of the symplectic leaves of the Poisson groupoid ... More
A simple model for explaining Galaxy Rotation CurvesApr 25 2018A new simple expression for the circular velocity of spiral galaxies is proposed and tested against HI Nearby Galaxy Survey (THINGS) data set. Its accuracy is compared with the one coming from MOND.
Stabilisation of dynamics of oscillatory systems by non-autonomous perturbationMar 30 2018Synchronisation and stability under periodic oscillatory driving are well-understood, but little is known about the effects of aperiodic driving, despite its abundance in nature. Here, we consider oscillators subject to driving with slowly varying frequency, ... More
Limitations of the asymptotic approach to dynamicsOct 09 2018Standard dynamical systems theory is centred around the coordinate-invariant asymptotic-time properties of autonomous systems. We identify three limitations of this approach. Firstly, we discuss how the traditional approach cannot take into account the ... More
A free parametrized TOV: Modified Gravity from Newtonian to Relativistic StarsJan 12 2016We test a free {\it ad hoc} parametrization of the Tolman-Oppenheimer-Volkoff (TOV) equation. We do not have in mind any specific extended theory of gravity (ETG) but each new parameter introduced has a physical interpretation. Our aim is fully pedagogical ... More
Fibre-wise linear Poisson structures related to W*-algebrasMar 03 2017In this paper we investigate fiber-wise linear complex Banach sub-Poisson structures defined canonically by the structure of a W*-algebra M. In particular we show that these structures are arranged in the short exact sequence of complex Banach sub-Poisson ... More
The Evolutionary Process of Image Transition in Conjunction with Box and Strip MutationAug 05 2016Evolutionary algorithms have been used in many ways to generate digital art. We study how evolutionary processes are used for evolutionary art and present a new approach to the transition of images. Our main idea is to define evolutionary processes for ... More
X-rays from a radio-loud compact BAL Quasar 1045+352 and the nature of outflows in radio-loud BAL QuasarsOct 05 2009Oct 28 2009We present new results on X-ray properties of radio loud broad absorption line (BAL) quasars and focus on broad-band spectral properties of a high ionization BAL (HiBAL) compact steep spectrum (CSS) radio-loud quasar 1045+352. This HiBAL quasar has a ... More
The nature of the intranight variability of radio-quiet quasarsFeb 29 2008We select a sample of 10 radio-quiet quasars with confirmed intranight optical variability and with available X-ray data. We compare the variability properties and the broad band spectral constraints to the predictions of intranight variability by three ... More
Intermittent activity of radio sources. Accretion instabilities and jet precessionOct 13 2010We consider the radiation pressure instability operating on short timescales 10^3 - 10^6 years in the accretion disk around a supermassive black hole as the origin of the intermittent activity of radio sources. We test whether this instability can be ... More
Drilled by the jet? XMM-Newton discovers a Compton-thick AGN in the GPS galaxy Mkn668Feb 26 2004We report the XMM-Newton discovery of the first Compton-thick obscured AGN in a Broad Line Radio Galaxy, the Gigahertz Peaked-Spectrum source Mkn668 (OQ+208). The remarkably flat 2-10 keV X-ray spectrum (observed photon index, \Gamma ~ 0.7), alongside ... More
High redshift radio quiet quasars - exploring the parameter space of accretion models. Part I: hot semi-spherical flowOct 07 2004Two families of models are currently considered to describe an accretion flow onto black holes and production of the observed X-ray radiation: (1) a standard cold accretion disk with a hot corona above it and (2) an outer truncated accretion disk with ... More
A Deep XMM-Newton Observation of the Quasar 3C 287Sep 26 2008We report on an XMM-Newton observation of the z=1.055 quasar and Giga-hertz Peaked Spectrum (GPS) source 3C 287. Our 62.3 ksec observation provides an exceptional X-ray view of a prominent member of this important subclass of active galactic nuclei (AGN). ... More