Results for "R. Bird"

total 129094took 0.13s
Influence of 3D plasmoid dynamics on the transition from collisional to kinetic reconnectionJun 12 2019Within the resistive magnetohydrodynamic model, high-Lundquist number reconnection layers are unstable to the plasmoid instability, leading to a turbulent evolution where the reconnection rate can be independent of the underlying resistivity. However, ... More
Electron-hole pair creation by atoms incident on a metal surfaceSep 30 2009Electron-hole pair creation by an adsorbate incident on a metal surface is described using \textit{ab initio} methods. The approach starts with standard first principles electronic structure theory, and proceeds to combine classical, quantum oscillator ... More
Dark matter pair-production in b -> s transitionsJan 12 2006Mar 05 2006The flavour-changing neutral current transition b \to s can serve as a sensitive probe of WIMP dark matter models, if the WIMP mass is under 2 GeV. In this work we extend our earlier analysis to a generic class of models where the interaction between ... More
A spin-polarised first principles study of short dangling bond wires on Si(001)Jan 30 2003Mar 06 2003Short dangling bond wires (DB wires), fabricated on H-terminated Si(001) surfaces, show patterns of displacement that depend on their length. We have performed density function calculations, with and without spin-polarisation, designed to investigate ... More
The Lifetime of FRIIs in Groups and Clusters: Implications for Radio-Mode FeedbackSep 13 2007Dec 09 2007We determine the maximum lifetime t_max of 52 FRII radio sources found in 26 central group galaxies from cross correlation of the Berlind SDSS group catalog with the VLA FIRST survey. Mock catalogs of FRII sources were produced to match the selection ... More
Electronic damping of molecular motion at metal surfacesSep 30 2009A method for the calculation of the damping rate due to electron-hole pair excitation for atomic and molecular motion at metal surfaces is presented. The theoretical basis is provided by Time Dependent Density Functional Theory (TDDFT) in the quasi-static ... More
Soliton effects in dangling-bond wires on Si(001)Jan 30 2003Dangling bond wires on Si(001) are prototypical one dimensional wires, which are expected to show polaronic and solitonic effects. We present electronic structure calculations, using the tight binding model, of solitons in dangling-bond wires, and demonstrate ... More
Simulating the Carbon Footprint of Galactic HalosDec 07 2015Jul 27 2016We compare simulations, including the Illustris simulations, to observations of CIV and CII absorption at z=2-4. These are the CIV column density distribution function in the column density range $10^{12} - 10^{15}$ cm$^{-2}$, the CIV equivalent width ... More
The USNO-B CatalogOct 31 2002USNO-B is an all-sky catalog that presents positions, proper motions, magnitudes in various optical passbands, and star/galaxy estimators for 1,042,618,261 objects derived from 3,643,201,733 separate observations. The data were obtained from scans of ... More
A lexical database tool for quantitative phonological researchJul 22 1997A lexical database tool tailored for phonological research is described. Database fields include transcriptions, glosses and hyperlinks to speech files. Database queries are expressed using HTML forms, and these permit regular expression search on any ... More
Constraints on ionising photon production from the large-scale Lyman-alpha forestJul 23 2014Sep 19 2014Recent work has shown that the z~2.5 Lyman-alpha forest on large scales encodes information about the galaxy and quasar populations that keep the intergalactic medium photoionized. We present the first forecasts for constraining the populations with data ... More
Galactic Positrons as a Probe of Large Extra DimensionsDec 24 2008Dec 24 2008In the last decade, there has been increased interest in the possibility that the Universe contains large additional dimensions. In this article it is proposed that the Kaluza-Klein modes which are predicted to exist in such models will be trapped in ... More
The Minimal Model of Radion Mediated Dark MatterDec 24 2008Based on the results from numerous astrophysics experiments, it is currently believed that the majority of matter in the Universe is in some unknown form, known as dark matter. In the past it has been common to model dark matter as a massive particle ... More
Computational PhonologyApr 10 2002Phonology, as it is practiced, is deeply computational. Phonological analysis is data-intensive and the resulting models are nothing other than specialized data structures and algorithms. In the past, phonological computation - managing data and developing ... More
The upgrade of the LHCb Vertex LocatorOct 03 2014Nov 10 2014The LHCb experiment is set for a significant upgrade, which will be ready for Run 3 of the LHC in 2020. This upgrade will allow LHCb to run at a significantly higher instantaneous luminosity and collect an integrated luminosity of $50\,\text{fb}^{-1}$ ... More
Two definable subcategories of maximal Cohen-Macaulay modulesApr 18 2019Apr 19 2019Over a Cohen-Macaulay ring we consider two extensions of the maximal Cohen-Macaulay modules from the viewpoint of definable subcategories, which are closed under direct limits, direct products and pure submodules. After describing these categories, we ... More
The Early Universe as a Probe of New PhysicsDec 24 2008The Standard Model of Particle Physics has been verified to unprecedented precision in the last few decades. However there are still phenomena in nature which cannot be explained, and as such new theories will be required. Since terrestrial experiments ... More
Two definable subcategories of maximal Cohen-Macaulay modulesApr 18 2019Over a Cohen-Macaulay ring we consider two extensions of the maximal Cohen-Macaulay modules from the viewpoint of definable subcategories, which are closed under direct limits, direct products and pure submodules. After describing these categories, we ... More
PhonologyApr 11 2002Phonology is the systematic study of the sounds used in language, their internal structure, and their composition into syllables, words and phrases. Computational phonology is the application of formal and computational techniques to the representation ... More
INTEGRAL discovery of unusually long broad-band X-ray activity from the Supergiant Fast X-ray Transient IGR J18483-0311Feb 16 2015We report on a broad-band X-ray study (0.5-250 keV) of the Supergiant Fast X-ray Transient IGR J18483-0311 using archival INTEGRAL data and a new targeted XMM-Newton observation. Our INTEGRAL investigation discovered for the first time an unusually long ... More
Newns-Anderson model of chemicurrents in H/Cu and H/AgApr 16 2008The excitation of the electronic system induced by the adsorption of a hydrogen atom on the (111) surfaces of copper and silver is investigated using the time-dependent, mean-field Newns-Anderson model. Parameters for the model are obtained by fitting ... More
Minimally Parametric Constraints on the Primordial Power Spectrum from Lyman-alphaMay 21 2010Current analyses of the Lyman-alpha forest assume that the primordial power spectrum of density perturbations obeys a simple power law, a strong theoretical assumption which should be tested. Employing a large suite of numerical simulations which drop ... More
Automated tone transcriptionOct 24 1994Oct 25 1994In this paper I report on an investigation into the problem of assigning tones to pitch contours. The proposed model is intended to serve as a tool for phonologists working on instrumentally obtained pitch data from tone languages. Motivation and exemplification ... More
Non-Ergodicity & Microscopic Symmetry Breaking of the Conductance Fluctuations in Disordered Mesoscopic GrapheneMar 28 2012Oct 18 2012We show a dramatic deviation from ergodicity for the conductance fluctuations in graphene. In marked contrast to the ergodicity of dirty metals, fluctuations generated by varying magnetic field are shown to be much smaller than those obtained when sweeping ... More
The INTEGRAL/IBIS AGN catalogue: an updateApr 21 2016Apr 27 2016In the most recent IBIS survey based on observations performed during the first 1000 orbits of INTEGRAL, are listed 363 high energy emitters firmly associated with AGN, 107 of which are reported here for the first time. We have used X-ray data to image ... More
Chasing extreme blazars with INTEGRALFeb 11 2013Within the blazar population, hard X-ray selected objects are of particular interest as they tend to lie at each end of the blazar sequence. In particular, flat spectrum radio quasars located at high redshifts display the most powerful jets, the largest ... More
INTEGRAL view of the Extragalactic SkyDec 21 2011Presented in this work is the most comprehensive INTEGRAL AGN sample: it includes 272 active galaxies for which optical identifications and redshifts are available. 2-10 keV fluxes and column density measurements are also collected for all the sample ... More
Energy loss of atoms at metal surfaces due to electron-hole pair excitations: First-principles theory of "chemicurrents"Sep 30 2009A method is presented for calculating electron-hole pair excitation due to an incident atom or molecule interacting with a metal surface. Energy loss is described using an \textit{ab initio} approach that obtains a position-dependent friction coefficient ... More
IGR J17354-3255 as a candidate intermediate SFXT possibly associated with the transient MeV AGL J1734-3310Jun 21 2011We present spectral and temporal results from INTEGRAL long-term monitoring of the unidentified X-ray source IGR J17354-3255. We show that it is a weak persistent hard X-ray source spending a major fraction of the time in an out-of-outburst state with ... More
The counterpart/s of IGR J20159+3713/SWIFT J2015.9+3715: dissecting a complex region with emission from keV to TeVOct 29 2013We report on the identification of a new soft gamma-ray source, namely IGR J20159+3713/SWIFT J2015.9+3715, first detected by INTEGRAL/IBIS and then confirmed by Swift/BAT. The source, which has an observed 20-100 keV flux in the range (0.7-1.4) x 10^(-11) ... More
Systematic effects induced on IBIS detectors by background and inhomogeneity of the spatial responseSep 15 2003The spatial distribution of the background events may affect the source detection capability of IBIS at high energies (> 200 keV) for both ISGRI and PICsIT layers. The observed background is found to be variable and spatially structured, and in some cases ... More
A macroscopic scale model of bacterial flagellar bundlingDec 21 2003Escherichia coli and other bacteria use rotating helical filaments to swim. Each cell typically has about four filaments, which bundle or disperse depending on the sense of motor rotation. To study the bundling process, we built a macroscopic scale model ... More
X-ray, optical and infrared investigation of the candidate Supergiant Fast X-ray Transient IGR J18462-0223May 07 2013We report on a broad-band X-ray study (0.5-60 keV) of the poorly known candidate Supergiant Fast X-ray Transient (SFXT) IGR J18462-0223, and on optical and near-infrared (NIR) followup observations of field objects. The out-of-outburst X-ray state has ... More
Five new INTEGRAL unidentified hard X-Ray sources uncovered by ChandraJun 23 2010The IBIS imager on board INTEGRAL, with a sensitivity better than a mCrab in deep observations and a point source location accuracy of the order of few arcminutes, has localized so far 723 hard X-ray sources in the 17--100 keV energy band, of which a ... More
Periodic Variability During the X-ray Decline of 4U 1636-53May 10 2005We report the onset of a large amplitude, statistically significant periodicity (~46 d) in the RXTE/ASM data of the prototype X-ray burster 4U 1636-53, the X-ray flux of which has been gradually declining over the last four years. This behaviour is remarkably ... More
Swift/XRT observations of unidentified INTEGRAL/IBIS sourcesDec 08 2009Dec 10 2009The 4th IBIS/ISGRI survey lists 723 hard X-ray sources many still unidentified. We cross-correlated the list of the sources included in the 4th IBIS catalogue with the Swift/XRT data archive, finding a sample of 20 objects for which XRT data could help ... More
Swift/XRT observations of newly discovered INTEGRAL sourcesApr 16 2013With respect to the recent INTEGRAL/IBIS 9-year Galactic Hard X-ray Survey (Krivonos et al. 2012), we use archival Swift/XRT observations in conjunction with multi-wavelength information to discuss the counterparts of a sample of newly discovered objects. ... More
Swift/XRT follow-up observations of unidentified INTEGRAL/IBIS sourcesMar 05 2010Many sources listed in the 4th IBIS/ISGRI survey are still unidentified, i.e. lacking an X-ray counterpart or simply not studied at lower energies (< 10 keV). The cross-correlation between the list of IBIS sources in the 4th catalogue and the Swift/XRT ... More
HESS J1616-508: likely powered by PSR J1617-5055Jul 05 2007HESS J1616-508 is one of the brightest emitters in the TeV sky. Recent observations with the IBIS/ISGRI telescope on board the INTEGRAL spacecraft have revealed that a young, nearby and energetic pulsar, PSR J1617-5055, is a powerful emitter of soft gamma-rays ... More
Voltage-induced suppression of weak localization in grapheneFeb 22 2017Feb 28 2018In this theoretical study, we explore the manner in which the quantum correction due to weak localization is suppressed in weakly-disordered graphene, when it is subjected to the application of a non-zero voltage. Using a nonequilibrium Green function ... More
IGR J12319-0749: evidence for another extreme blazar found with INTEGRALMay 14 2012We report on the identification of a new soft gamma-ray source, IGR J12319-0749, detected with the IBIS imager on board the INTEGRAL satellite. The source, which has an observed 20-100 keV flux of ~8.3 x 10^{-12} erg cm^{-2} s^{-1}, is spatially coincident ... More
A Mass Model for Estimating the Gamma Ray Background of the Burst and Transient Source ExperimentNov 19 2002Orbiting x-ray and gamma ray instruments are subject to large background count rates due to local particle fluxes in the space environment. The ability of an instrument to make calibrated measurements of the flux from a source of interest is highly dependent ... More
The peculiar high-mass X-ray binary 1ES 1210-646Jan 04 2010Using data collected with the BeppoSAX, INTEGRAL and Swift satellites, we report and discuss the results of a study on the X-ray emission properties of the X-ray source 1ES 1210-646, recently classified as a high-mass X-ray binary through optical spectroscopy. ... More
INTEGRAL/IBIS and Swift/XRT observations of hard cataclysmic variablesOct 10 2008The analysis of the third INTEGRAL/IBIS survey has revealed several new cataclysmic variables, most of which turned out to be intermediate polars, thus confirming that these objects are strong emitters in hard X-rays. Here we present high energy spectra ... More
INTEGRAL and Swift/XRT observations of the SFXT IGR J16479-4514: from quiescence to fast flaring activityMay 05 2008Context: IGR J16479-4514 is a fast X-ray transient known to display flares lasting typically a few hours. Recently, its counterpart has been identified with a supergiant star, therefore the source can be classified as member of the newly discovered class ... More
Broadband study of hard X-ray selected absorbed AGNNov 08 2011[Abridged]We report on the broadband X-ray properties of a complete sample of absorbed Seyfert galaxies hard X-ray selected with INTEGRAL. The sample is composed of 33 sources: 15 are newly discovered above 20 keV while 18 are already known AGN. For 17 ... More
Broadband X-ray properties of absorbed AGNDec 20 2011In this paper we report on the broadband X-ray properties of a complete sample of 33 absorbed Seyfert galaxies hard X-ray selected with integral. The high quality broadband spectra obtained with both xmm, and integral-IBIS data are well reproduced with ... More
Review on Active Galactic Nuclei at hard X-ray energiesFeb 11 2013Hard X-ray surveys are an important tool for the study of active galactic nuclei (AGN): they provide almost an unbiased view of absorption in the extragalactic population, allow the study of spectral features such as reflection and high energy cut-off ... More
The power spectrum of the Milky Way: Velocity fluctuations in the Galactic diskOct 29 2014Feb 16 2015We investigate the kinematics of stars in the mid-plane of the Milky Way on scales between 25 pc and 10 kpc with data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE), the Radial Velocity Experiment (RAVE), and the Geneva-Copenhagen ... More
The Magellanic Bridge: evidence for a population of X-ray binariesDec 15 2009INTEGRAL observations of the Small Magellanic Cloud region have resulted in the serendipitous detection of two transient hard X-ray sources in the Magellanic Bridge. In this paper we present the timing and spectral characteristics of these sources across ... More
Contrasting behaviour from two Be/X-ray binary pulsars: insights into differing neutron star accretion modesApr 29 2013In this paper we present the identification of two periodic X-ray signals coming from the direction of the Small Magellanic Cloud (SMC). On detection with the Rossi X-ray Timing Explorer (RXTE), the 175.4s and 85.4s pulsations were considered to originate ... More
Building an Open Language Archives Community on the OAI FoundationFeb 14 2003The Open Language Archives Community (OLAC) is an international partnership of institutions and individuals who are creating a worldwide virtual library of language resources. The Dublin Core (DC) Element Set and the OAI Protocol have provided a solid ... More
Querying Databases of Annotated SpeechApr 11 2002Annotated speech corpora are databases consisting of signal data along with time-aligned symbolic `transcriptions'. Such databases are typically multidimensional, heterogeneous and dynamic. These properties present a number of tough challenges for representation ... More
Substructure in Clusters and Central Galaxy Peculiar VelocitiesFeb 23 1994Formation theories for central dominant galaxies in clusters require them to be located at the minimum of the cluster gravitational potential. However, 32\% (8 out of 25) of the clusters with more than 50 measured redshifts have central galaxies with ... More
A Grid Based Architecture for High-Performance NLPAug 05 2003We describe the design and early implementation of an extensible, component-based software architecture for natural language engineering applications which interfaces with high performance distributed computing services. The architecture leverages existing ... More
The Open Language Archives Community: An infrastructure for distributed archiving of language resourcesJun 10 2003New ways of documenting and describing language via electronic media coupled with new ways of distributing the results via the World-Wide Web offer a degree of access to language resources that is unparalleled in history. At the same time, the proliferation ... More
Grid-Enabling Natural Language Engineering By StealthApr 22 2003We describe a proposal for an extensible, component-based software architecture for natural language engineering applications. Our model leverages existing linguistic resource description and discovery mechanisms based on extended Dublin Core metadata. ... More
A Formal Framework for Linguistic Annotation (revised version)Oct 26 2000`Linguistic annotation' covers any descriptive or analytic notations applied to raw language data. The basic data may be in the form of time functions - audio, video and/or physiological recordings - or it may be textual. The added notations may include ... More
Extending Dublin Core Metadata to Support the Description and Discovery of Language ResourcesAug 14 2003As language data and associated technologies proliferate and as the language resources community expands, it is becoming increasingly difficult to locate and reuse existing resources. Are there any lexical resources for such-and-such a language? What ... More
A Formal Framework for Linguistic AnnotationMar 02 1999`Linguistic annotation' covers any descriptive or analytic notations applied to raw language data. The basic data may be in the form of time functions -- audio, video and/or physiological recordings -- or it may be textual. The added notations may include ... More
Annotation Graphs and Servers and Multi-Modal Resources: Infrastructure for Interdisciplinary Education, Research and DevelopmentApr 10 2002Annotation graphs and annotation servers offer infrastructure to support the analysis of human language resources in the form of time-series data such as text, audio and video. This paper outlines areas of common need among empirical linguists and computational ... More
Giant Lyman-Alpha Nebulae in the Illustris SimulationMay 11 2016Several `giant' Lyman-$\alpha$ (Ly$\alpha$) nebulae with extent $\gtrsim 300\,$kpc and observed Ly$\alpha$ luminosity of $\gtrsim 10^{44}\,{\rm erg}\,{\rm s}^{-1}\,{\rm cm}^{-2}\,{\rm arcsec}^{-2}$ have recently been detected, and it has been speculated ... More
The Impact of Galactic Feedback on the Circumgalactic MediumJan 09 2015Galactic feedback strongly affects the way galactic environments are enriched. We examine this connection by performing a suite of cosmological hydrodynamic simulations, exploring a range of parameters based on the galaxy formation model developed in ... More
Seven Dimensions of Portability for Language Documentation and DescriptionApr 10 2002The process of documenting and describing the world's languages is undergoing radical transformation with the rapid uptake of new digital technologies for capture, storage, annotation and dissemination. However, uncritical adoption of new tools and technologies ... More
NLTK: The Natural Language ToolkitMay 17 2002NLTK, the Natural Language Toolkit, is a suite of open source program modules, tutorials and problem sets, providing ready-to-use computational linguistics courseware. NLTK covers symbolic and statistical natural language processing, and is interfaced ... More
An Integrated Framework for Treebanks and Multilayer AnnotationsApr 03 2002Treebank formats and associated software tools are proliferating rapidly, with little consideration for interoperability. We survey a wide variety of treebank structures and operations, and show how they can be mapped onto the annotation graph model, ... More
Annotation graphs as a framework for multidimensional linguistic data analysisJul 05 1999In recent work we have presented a formal framework for linguistic annotation based on labeled acyclic digraphs. These `annotation graphs' offer a simple yet powerful method for representing complex annotation structures incorporating hierarchy and overlap. ... More
Discussion of: Statistical analysis of an archeological find--skeptical counting challenges to an archaeological findApr 01 2008Discussion of ``Statistical analysis of an archeological find'' by Andrey Feuerverger [arXiv:0804.0079]
Many uses, many annotations for large speech corpora: Switchboard and TDT as case studiesJul 13 2000This paper discusses the challenges that arise when large speech corpora receive an ever-broadening range of diverse and distinct annotations. Two case studies of this process are presented: the Switchboard Corpus of telephone conversations and the TDT2 ... More
The Effects of Substructure on Galaxy Cluster Mass DeterminationsMar 08 1995Mar 09 1995Although numerous studies of individual galaxy clusters have demonstrated the presence of significant substructure, previous studies of the distribution of masses of galaxy clusters determined from optical observations have failed to explicitly correct ... More
Giant Lyman-Alpha Nebulae in the Illustris SimulationMay 11 2016Dec 19 2016Several `giant' Lyman-$\alpha$ (Ly$\alpha$) nebulae with extent $\gtrsim 300\,$kpc and observed Ly$\alpha$ luminosity of $\gtrsim 10^{44}\,{\rm erg}\,{\rm s}^{-1}\,{\rm cm}^{-2}\,{\rm arcsec}^{-2}$ have recently been detected, and it has been speculated ... More
The OLAC Metadata Set and Controlled VocabulariesMay 21 2001As language data and associated technologies proliferate and as the language resources community rapidly expands, it has become difficult to locate and reuse existing resources. Are there any lexical resources for such-and-such a language? What tool can ... More
Muon Hunter: a Zooniverse projectFeb 24 2018The large datasets and often low signal-to-noise inherent to the raw data of modern astroparticle experiments calls out for increasingly sophisticated event classification techniques. Machine learning algorithms, such as neural networks, have the potential ... More
The nature of the ASCA/INTEGRAL source AX J183039-1002: a new Compton-thick AGN?Jan 16 2009We report on the identification of the X/soft gamma-ray source AX J183039-1002 detected with ASCA and INTEGRAL/IBIS. The source, which has an observed 20-100 keV flux of about 8.6 x 10^-11 erg/cm^2/s, is inside a diffuse radio supernova remnant (SNR) ... More
SWIFT/XRT follow-up observations of INTEGRAL AGNsOct 12 2006In five years of operation, data from INTEGRAL has been used to discover a large number of gamma-ray sources, a substantial fraction of which have turned out to be active galactic nuclei (AGN). Recently Bassani et al. (2006) have presented a sample of ... More
Using the ROSAT Bright Source Catalogue to find Counterparts for IBIS/ISGRI Survey SourcesFeb 08 2005The IBIS/ISGRI first year galactic plane survey has produced a catalogue containing 123 hard X-ray sources visible down to a flux limit of a few milliCrabs. The point source location accuracy of typically 1-3 arcminutes has allowed the counterparts for ... More
IGR J16393-4643: a new heavily-obscured X-ray pulsarOct 05 2005Oct 06 2005An analysis of the high-energy emission from IGR J16393-4643 (=AX J1639.0-4642) is presented using data from INTEGRAL and XMM-Newton. The source is persistent in the 20-40 keV band at an average flux of 5.1x10^-11 ergs/cm2/s, with variations in intensity ... More
Evidence of polarisation in the prompt gamma-ray emission from GRB 930131 and GRB 960924May 05 2005The true nature of the progenitor to GRBs remains elusive; one characteristic that would constrain our understanding of the GRB mechanism considerably is gamma-ray polarimetry measurements of the initial burst flux. We present a method that interprets ... More
Narrow Line Seyfert 1 galaxies at hard X-raysJun 15 2011Narrow Line Seyfert 1 (NLSy1) galaxies are a peculiar class of type 1 AGN (BLSy1). The X-ray properties of individual objects belonging to this class are often extreme and associated with accretion at high Eddington ratios. Here we present a study on ... More
Unveiling the nature of INTEGRAL objects through optical spectroscopy. II. The nature of four unidentified sourcesNov 07 2005We present the results of our optical spectrophotometric campaign ongoing at the Astronomical Observatory of Bologna in Loiano (Italy) on hard X-ray sources detected by INTEGRAL. We observed spectroscopically the putative optical counterparts of four ... More
INTEGRAL and Swift observations of the supergiant fast X-ray transient AXJ1845.0-0433=IGRJ18450-0435Oct 30 2006Oct 31 2006Context: AXJ1845.0-0433 was discovered by ASCA in 1993 during fast outburst activity characterized by several flares on short timescales. Up to now, the source was not detected again by any X-ray mission. Its optical counterpart is suggested to be an ... More
Tracing chemical evolution over the extent of the Milky Way's Disk with APOGEE Red Clump StarsSep 11 2014We employ the first two years of data from the near-infrared, high-resolution SDSS-III/APOGEE spectroscopic survey to investigate the distribution of metallicity and alpha-element abundances of stars over a large part of the Milky Way disk. Using a sample ... More
A review of progress in the physics of open quantum systems: theory and experimentJul 30 2015Nov 05 2015This Report explores recent advances in our understanding of the physics of open quantum systems (OQSs) which consist of some localized region that is coupled to an external environment. Examples of such systems may be found in numerous areas of physics ... More
Comment on ``New Class of Resonances at the Edge of the Two-Dimensional Electron Gas:'' self-consistent electronic structureNov 01 1996Self-consistent electronic structure calculations, for devices recently fabricated and studied by Zhitenev et al. for capacitance spectroscopy in the quantum Hall regime, demonstrate that reproducible resonances in the coupling between adiabatically free ... More
Fading Features Found in the Kinematics of the Far-Reaching Milky Way Stellar HaloJul 01 2015We test the long-term kinematical stability of a Galactic stellar halo model, due to Kafle, et al. (2012), who study the kinematics of approximately 5000 blue horizontal branch (BHB) stars in the Sloan Digital Sky Survey (SDSS). The velocity dispersion ... More
An efficient implementation of massive neutrinos in non-linear structure formation simulationsSep 03 2012Nov 19 2012Massive neutrinos make up a fraction of the dark matter, but due to their large thermal velocities, cluster significantly less than cold dark matter (CDM) on small scales. An accurate theoretical modelling of their effect during the non-linear regime ... More
IGR J16194-2810: a new symbiotic X-ray binaryApr 27 2007Jun 22 2007We here report on the multiwavelength study which led us to the identification of X-ray source IGR J16194-2810 as a new Symbiotic X-ray Binary (SyXB), that is, a rare type of Low Mass X-ray Binary (LMXB) composed of a M-type giant and a compact object. ... More
Flat-Fielding BATSE Occultation Data for use in a Hard X-Ray All Sky SurveyJan 03 2001The BATSE mission aboard CGRO can be used to observe hard X-ray sources by using the Earth occultation method. This method relies on measuring a step in the count rate profile in each BATSE detector as a source rises above or sets below the Earth's limb. ... More
First high energy observations of Narrow Line Seyfert 1s with INTEGRAL/IBISJun 30 2008Jul 08 2008Narrow Line Seyfert 1 galaxies (NLS1) are very interesting objects which display peculiar properties when compared to their broad line analogues (BLS1). Although well studied in many wavebands, their behaviour at >10 keV is poorly studied and yet important ... More
The broad-band X-ray spectrum of the blazar PKS B1830-211 by Chandra and INTEGRALApr 06 2005In this paper we present a broad-band study of the X-ray emission of the blazar PKS1830-211 based on Chandra and Integral observations. Notwithstanding the high redshift (z=2.507), it is a bright X-ray source (F(2-10 keV)~10^{-11} erg cm^{-2} s^{-1}), ... More
Integral/Ibis Census of the Sky Beyond 100 kevAug 08 2006We report on the first census of INTEGRAL/IBIS detections ($\gtrsim 4\sigma$ significance) above 100 keV based on the Core Program and public Open time observations up to April 2005. There are 49 sources detected in the 100-150 keV band of which 14 are ... More
Swift/XRT follow-up observations of TeV sources of the HESS Inner Galaxy surveyJul 15 2006In order to provide a firm identification of the newly discovered Galactic TeV sources, a search for counterparts in a broad band from soft X-ray to soft gamma-rays is crucial as data in these wavebands allow us to distinguish between different types ... More
The AGN nature of three INTEGRAL sources: IGR J18249-3243, IGR J19443+2117 and IGR J22292+6647Nov 14 2008The third INTEGRAL/IBIS survey has revealed several new hard X-ray sources, which are still unclassified. To identify these sources, we need to find their counterparts at other wavelengths and then study their nature. The capability of XRT on board Swift ... More
Probing the nature of IGR J16493-4348: Spectral and temporal analysis of the 1-100 keV emissionDec 13 2007IGR J16493-4348 was one of the first new sources to be detected by the INTEGRAL gamma-ray telescope in the 18-100 keV energy band. Based upon spatial coincidence the source was originally associated with the free radio pulsar PSR J1649-4349. Presented ... More
The BATSE 9 year histories of the brightest AGNAug 24 2004The Burst and Transient Source Experiment (BATSE) aboard CGRO monitored the whole sky through 8 NaI(Tl) crystal scintillators sensitive in the 20 keV - 2 MeV energy band continuously from April 1991 until June 2000. Results are presented on the long term ... More
IGR J22517+2218=MG3 J225155+2217: a new gamma-ray lighthouse in the distant UniverseSep 19 2007We report on the identification of a new soft gamma ray source, namely IGR J22517+2218, detected with IBIS/INTEGRAL. The source, which has an observed 20-100 keV flux of ~4 x10^-11 erg cm-2 s-1, is spatially coincident with MG3 J225155+2217, a quasar ... More
The AGN nature of 11 out of 12 Swift/RXTE unidentified sources through optical and X-ray spectroscopyJun 23 2007The Swift Burst Alert Telescope (BAT) is performing a high Galactic latitude survey in the 14-195 keV band at a flux limit of ~10^{-11} erg cm^{-2} s^{-1}, leading to the discovery of new high energy sources, most of which have not so far been properly ... More
Multi-wavelength observations of the Be/X-ray binary IGR J01217-7257 (=SXP 2.16) during outburstDec 02 2016We present simultaneous, multi-wavelength observations of the Small Magellanic Cloud Be/XRB IGR J01217-7257 (=SXP 2.16) during outbursts in 2014, 2015 and 2016. We also present the results of RXTE observations of the Small Magellanic Cloud during which ... More
Be/X-ray binary SXP6.85 undergoes large Type II outburst in the Small Magellanic CloudDec 15 2009The Small Magellanic Cloud (SMC) Be/X-ray binary pulsar SXP6.85 = XTE J0103-728 underwent a large Type II outburst beginning on 2008 August 10. The source was consistently seen for the following 20 weeks (MJD = 54688 - 54830). We present X-ray timing ... More
High-redshift blazar identification for Swift J1656.3-3302Jan 18 2008We report on the high-redshift blazar identification of a new gamma-ray source, Swift J1656.3-3302, detected with the BAT imager onboard the Swift satellite and the IBIS instrument on the INTEGRAL satellite. Follow-up optical spectroscopy has allowed ... More