Results for "S. Buson"

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The mid-infrared colour-magnitude relation of early-type galaxies in the Coma cluster as measured by Spitzer-IRSAug 21 2008Oct 15 2008We use 16 micron, Spitzer-IRS, blue peakup photometry of 50 early-type galaxies in the Coma cluster to define the mid-infrared colour-magnitude relation. We compare with recent simple stellar population models that include the mid-infrared emission from ... More
Cascading Constraints from Neutrino Emitting Blazars: The case of TXS 0506+056Dec 13 2018We present a procedure to generally constrain the environments of neutrino-producing sites in photomeson production models of jetted Active Galactic Nuclei (AGN) where any origin of the dominant target photon field can be accommodated. For this purpose ... More
Fermi-LAT Detection of a Hard Spectrum Flare from the Gravitationally Lensed Blazar B0218+357Feb 10 2015The Fermi-LAT has observed new gamma-ray flares from the blazar B0218+357 during July 2014. While no significant change in the gamma-ray spectrum has been previously observed through the flaring phase in late-2012, during this recent high activity the ... More
Flaring gamma-ray AGNs seen with the FERMI LATMar 10 2013Mar 12 2013In the first 3.5 years of operations the Fermi LAT detected several sources with daily fluxes brighter than F(E>100MeV) > 10^{-6} ph/cm^2/s, the threshold set by the Fermi Collaboration for issuing an Astronomer Telegram. We focus the attention on these ... More
The mid-UV population of the nucleus and the bulk of the post-merger NGC 3610Aug 05 2010The very center of NGC~3610, a clearly disturbed giant elliptical generally assumed to be a post-merger remnant, appears dominated in the mid-UV (2500-3200 A spectral region) by a stellar population markedly different from that dominating the bulk of ... More
Neutrinos, Cosmic Rays and the MeV BandMar 13 2019The possible association of the blazar TXS 0506+056 with a high-energy neutrino detected by IceCube holds the tantalizing potential to answer three astrophysical questions: 1. Where do high-energy neutrinos originate? 2. Where are cosmic rays produced ... More
Search for Gamma-ray Emission from Galactic Novae with the Fermi-LATOct 12 2017Context. A number of novae have been found to emit high-energy gamma rays (>100 MeV). However, the origin of this emission is not yet understood. We report on the search for gamma-ray emission from 75 optically-detected Galactic novae in the first 7.4 ... More
Multiwavelength evidence for a 15-year periodic activity in the symbiotic nova V1016 CygniJul 01 2002The ~15.1 years period found in the long-term UBV photoelectric and photographic photometry of the symbiotic nova V1016 Cyg is detected also in the (J-K) colour index and in the UV continuum and emission line fluxes from IUE and HUT spectra. It could ... More
Coordinated UV-optical observations of quasars: the evolution of the Lyman absorptionOct 14 1992The average flux decrement shortward the Ly$_{\alpha}$ emission, due to the well-known ``forest'' of absorptions, has been measured in the spectra of 8 quasars. Quasi-simultaneous optical and IUE observations of the two low redshift quasars PKS 0637--75 ... More
High-Energy Polarimetry - a new window to probe extreme physics in AGN jetsMar 11 2019The constantly improving sensitivity of ground-based and space-borne observatories has made possible the detection of high-energy emission (X-rays and gamma-rays) from several thousands of extragalactic sources. Enormous progress has been made in measuring ... More
Supermassive black holes at high redshiftsMar 14 2019MeV blazars are the most luminous persistent sources in the Universe and emit most of their energy in the MeV band. These objects display very large jet powers and accretion luminosities and are known to host black holes with a mass often exceeding $10^9 ... More
The MAGIC view of PG 1553+113Oct 31 2011We present the results of five years (2005-2009) of MAGIC observations of the BL Lac object PG 1553+113 at very high energies (VHEs). Adding the new data set (2007-2009) to previous observations, this source becomes one of the best long-term followed ... More
Nearby early-type galaxies with ionized gas VI. The Spitzer-IRS viewOct 12 2010Jan 25 2011We present low resolution Spitzer-IRS spectra of 40 ETGs, selected from a sample of 65 ETGs showing emission lines in their optical spectra. We homogeneously extract the mid-infrared (MIR) spectra, and after the proper subtraction of a "passive" ETG template, ... More
Unusual PAH Emission in Nearby Early-Type Galaxies: A Signature of an Intermediate Age Stellar Population?Jul 30 2010We present the analysis of Spitzer-IRS spectra of four early-type galaxies, NGC 1297, NGC 5044, NGC 6868, and NGC 7079, all classified as LINERs in the optical bands. Their IRS spectra present the full series of H2 rotational emission lines in the range ... More
Early Type Galaxies in the Mid Infrared: a new flavor to their stellar populationsFeb 02 2007The mid infrared emission of early type galaxies traces the presence of intermediate age stellar populations as well as even tiny amounts of ongoing star formation. Here we discuss high S/N Spitzer IRS spectra of a sample of Virgo early type galaxies, ... More
Coincidence of a high-fluence blazar outburst with a PeV-energy neutrino eventFeb 05 2016Mar 03 2016The discovery of extraterrestrial very-high-energy neutrinos by the IceCube collaboration has launched a quest for the identification of their astrophysical sources. Gamma-ray blazars have been predicted to yield a cumulative neutrino signal exceeding ... More
Early Type Galaxies in the Mid InfraredJan 22 2007We are performing a systematic study of the properties of early-type galaxies in the mid infrared spectral region with the Spitzer Space Telescope. We present here high S/N Spitzer IRS spectra of 17 Virgo early-type galaxies. Thirteen objects of the sample ... More
MAGIC discovery and multiwavelength observations of the BL Lac 1ES 1727+502Aug 15 2013Blazars, active galactic nuclei whose jet axis is pointed towards the observer, constitute the most numerous class of extragalactic very high energy (VHE, E > 100\, GeV) gamma-ray emitters. The MAGIC experiment, a system of two Imaging Atmospheric Cherenkov ... More
Nearby early-type galaxies with ionized gas. The UV emission from GALEX observationsSep 10 2010We present GALEX far-ultraviolet (FUV, $\lambda_{eff}$=1538 \AA) and near-ultraviolet (NUV, $\lambda_{eff}$=2316 \AA) surface photometry of 40 early-type galaxies (ETGs) selected from a wider sample of 65 nearby ETGs showing emission lines in their optical ... More
The Star Formation History of the Virgo early-type galaxy NGC4435: the Spitzer Mid Infrared viewOct 11 2006We present a population synthesis study of NGC4435, an early-type Virgo galaxy interacting with NGC4438. We combine new spectroscopic observations obtained with the Spitzer Space Telescope IRS instrument with IRAC archival data and broad band data from ... More
The role of the synchrotron component in the mid infrared spectrum of M 87Sep 18 2009We study in detail the mid-infrared Spitzer-IRS spectrum of M 87 in the range 5 to 20 micron. Thanks to the high sensitivity of our Spitzer-IRS spectra we can disentangle the stellar and nuclear components of this active galaxy. To this end we have properly ... More
SPITZER IRS spectra of Virgo early type galaxies: detection of stellar silicate emissionFeb 01 2006We present high signal to noise ratio Spitzer Infrared Spectrograph observations of 17 Virgo early-type galaxies. The galaxies were selected from those that define the colour-magnitude relation of the cluster, with the aim of detecting the silicate emission ... More
The transformation of Spirals into S0 galaxies in the cluster environmentAug 19 2015We discuss the observational evidences of the morphological transformation of Spirals into S0 galaxies in the cluster environment exploiting two big databases of galaxy clusters: WINGS (0.04 < z < 0.07) and EDisCS (0.4 < z < 0.8). The most important results ... More
The SPITZER IRS view of stellar populations in Virgo early type galaxiesApr 04 2006We have obtained high S/N Spitzer IRS spectra of 17 Virgo early-type galaxies that lie on the colour-magnitude relation of passively evolving galaxies in the cluster. To flux calibrate these extended sources we have devised a new procedure that allows ... More
Studying flux variability of the BL Lac object 1ES0806+524 with MAGIC in a multi-wavelength contextAug 15 2013We present results of multi-wavelength (MWL) observations of the high-frequency-peaked BL Lacertae (HBL) object 1ES 0806+524 (z=0.138). Triggered by a high optical state, very high energy (VHE; E > 100 GeV) observations were carried out with the MAGIC ... More
Latest MAGIC discoveries pushing redshift boundaries in VHE AstrophysicsJun 14 2016The search for detection of gamma-rays from distant AGNs by Imaging Atmospheric Cherenkov Telescopes (IACTs) is challenging at high redshifts, not only because of lower flux due to the distance of the source, but also due to the consequent absorption ... More
The innermost region of the NGC 1023 Group: Insight into its evolutionApr 16 2012The NGC 1023 group is one of the most studied nearby groups. We want to give an insight into the evolution of its innermost region by means of ultraviolet observations and proper models. We used the FUV and NUV GALEX archival data as well as a large set ... More
New Candidate EHB Stars in the Open Cluster NGC 6791: Looking Locally into the UV-upturn PhenomenonSep 26 2005Relying on U,B imagery at the Italian Telescopio Nazionale Galileo (TNG), we report here the discovery of a sample of 13 new UV-bright post-HB candidate stars in the field of the galactic open cluster NGC 6791. Owing to its super-solar metal content ([Fe/H]>0.2 ... More
Unusual Flaring Activity in the Blazar PKS 1424-418 during 2008-2011Jul 01 2014Aug 07 2014Context. Blazars are a subset of active galactic nuclei (AGN) with jets that are oriented along our line of sight. Variability and spectral energy distribution (SED) studies are crucial tools for understanding the physical processes responsible for observed ... More
UB CCD photometry of the old, metal rich, open clusters NGC 6791, NGC 6819 and NGC 7142Sep 16 2013We report on a UV-oriented imaging survey in the fields of the old, metal-rich open clusters, NGC 6791, NGC 6819 and NGC 7142. These three clusters represent both very near and ideal stellar aggregates to match the distinctive properties of the evolved ... More
The Quest for the Dominant Stellar Population in the Giant Elliptical NGC 5018Oct 24 2000Newly obtained HST/WFPC2 images of the disturbed elliptical galaxy NGC 5018 show that the average amount of internal reddening due to the its complex ``dust web'' is as low as E(B-V)~0.02 within the IUE aperture, thus implying that its observed and intrinsic ... More
Search for cosmic-ray induced gamma-ray emission in Galaxy ClustersAug 26 2013Mar 24 2014Current theories predict relativistic hadronic particle populations in clusters of galaxies in addition to the already observed relativistic leptons. In these scenarios hadronic interactions give rise to neutral pions which decay into $\gamma$ rays, that ... More
Opportunities for Multimessenger Astronomy in the 2020sMar 11 2019Electromagnetic observations of the sky have been the basis for our study of the Universe for millennia, cosmic ray studies are now entering their second century, the first neutrinos from an astrophysical source were identified three decades ago, and ... More
Dark Matter Constraints from Observations of 25 Milky Way Satellite Galaxies with the Fermi Large Area TelescopeOct 02 2013Feb 19 2014The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered ... More
UGC 7639: a Dwarf Galaxy in the Canes Venatici I CloudJul 08 2015We want to get insight into the nature, i.e. the formation mechanism and the evolution, of UGC 7639, a dwarf galaxy in the Canes Venatici I Cloud (CVnIC). We used archival GALEX (FUV and NUV) and SDSS images, as well as Hyperleda and NED databases, to ... More
Stellar lifetime and ultraviolet properties of the old metal-rich Galactic open cluster NGC6791: a pathway to understand the UV upturn of elliptical galaxiesFeb 20 2012The evolutionary properties of the old metal-rich Galactic open cluster NGC6791 are assessed, based on deep UB photometry and 2Mass JK data. For 4739 stars in the cluster, bolometric luminosity and effective temperature have been derived from theoretical ... More
The Third Catalog of Active Galactic Nuclei Detected by the Fermi Large Area TelescopeJan 24 2015Aug 26 2015The third catalog of active galactic nuclei (AGNs) detected by the Fermi-LAT (3LAC) is presented. It is based on the third Fermi-LAT catalog (3FGL) of sources detected between 100 MeV and 300 GeV with a Test Statistic (TS) greater than 25, between 2008 ... More
PSR J1906+0722: An Elusive Gamma-ray PulsarAug 04 2015We report the discovery of PSR J1906+0722, a gamma-ray pulsar detected as part of a blind survey of unidentified Fermi Large Area Telescope (LAT) sources being carried out on the volunteer distributed computing system, Einstein@Home. This newly discovered ... More
Fermi Large Area Telescope Detection of Bright Gamma-ray Outbursts from a Peculiar Quasar 4C +21.35Jan 27 2011In this paper we report on the two-year-long Fermi-LAT observation of the peculiar blazar 4C +21.35 (PKS 1222+216). This source was in a quiescent state from the start of science operations of the Fermi Gamma-ray Space Telescope in 2008 August until 2009 ... More
A significant hardening and rising shape detected in the MeV/GeV nuFnu spectrum from the recently-discovered very-high-energy blazar S4 0954+65 during the bright optical flare in 2015 FebruaryApr 19 2016We report on Fermi Large Area Telescope (LAT) and multi-wavelength results on the recently-discovered very-high-energy (VHE, $E>$ 100 GeV) blazar S4 0954+65 ($z=0.368$) during an exceptionally bright optical flare in 2015 February. During the time period ... More
VHE gamma-ray emission from the FSRQs observed by the MAGIC telescopesMar 08 2013Among more than fifty blazars detected in very high energy (VHE, E>100GeV) gamma-rays, only three belong to the subclass of Flat Spectrum Radio Quasars (FSRQs): PKS 1510-089, PKS 1222+216 and 3C 279. The detection of FSRQs in the VHE range is challenging, ... More
Optical and IR observations of SN 2002dj: some possible common properties of fast expanding SNe IaMay 08 2008Jun 11 2008As part of the European Supernova Collaboration we obtained extensive photometry and spectroscopy of the type Ia SN 2002dj covering epochs from 11 days before to nearly two years after maximum. Detailed optical and near-infrared observations show that ... More
Constraining Dark Matter Models from a Combined Analysis of Milky Way Satellites with the Fermi Large Area TelescopeAug 17 2011Dec 12 2011Satellite galaxies of the Milky Way are among the most promising targets for dark matter searches in gamma rays. We present a search for dark matter consisting of weakly interacting massive particles, applying a joint likelihood analysis to 10 satellite ... More
Binary Millisecond Pulsar Discovery via Gamma-Ray PulsationsNov 06 2012Nov 26 2012Millisecond pulsars, old neutron stars spun-up by accreting matter from a companion star, can reach high rotation rates of hundreds of revolutions per second. Until now, all such "recycled" rotation-powered pulsars have been detected by their spin-modulated ... More
The spectrum of isotropic diffuse gamma-ray emission between 100 MeV and 820 GeVOct 14 2014The {\gamma}-ray sky can be decomposed into individually detected sources, diffuse emission attributed to the interactions of Galactic cosmic rays with gas and radiation fields, and a residual all-sky emission component commonly called the isotropic diffuse ... More
The Real-Time Analysis of the Cherenkov Telescope Array ObservatoryJul 24 2013The Cherenkov Telescope Array (CTA) Observatory must be capable of issuing fast alerts on variable and transient sources to maximize the scientific return. This will be accomplished by means of a Real-Time Analysis (RTA) pipeline, a key system of the ... More
Gamma-ray observations of the Orion Molecular Clouds with the Fermi Large Area TelescopeJul 03 2012We report on the gamma-ray observations of giant molecular clouds Orion A and B with the Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope. The gamma-ray emission in the energy band between \sim100 MeV and \sim100 GeV is predicted ... More
Field Camera Unit for WSO-UV: Phase A Study ReportDec 06 2007World Space Observatory UltraViolet (WSO-UV) is a multipurpose space observatory, made by a 170 cm aperture telescope, capable of UV high-resolution spectroscopy, long slit low-resolution spectroscopy, and deep UV and optical imaging. With a nominal mission ... More
Signatures of recent star formation in ring S0 galaxiesJan 05 2011We present a study of the stellar populations of ring and/or arm-like structures in a sample of S0 galaxies using GALEX far- and near-ultraviolet imaging and SDSS optical data. Such structures are prominent in the UV and reveal recent star formation. ... More
The UV window on counter rotating ETGs: insight from SPH simulations with chemo-photometric implementationMay 15 2014The Galaxy Evolution Explorer (GALEX) detected ultraviolet emission in about 50% of multi-spin early-type galaxies (ETGs), suggesting the occurrence of a recent rejuvenation episode connected to the formation of these kinematical features. With the aim ... More
NGC 3934: a shell galaxy in a compact galaxy environmentAug 30 2011We investigate the NGC 3933 poor galaxy association, that contains NGC 3934, which is classified as a polar-ring galaxy. The multi-band photometric analysis of NGC 3934 allows us to investigate the nature of this galaxy and to re-define the NGC 3933 group ... More
The GALEX UV emission in shell galaxiesJan 15 2008Shell galaxies are widely considered the debris of recent accretion/merging episodes. Their high frequency in low density environment suggests that such episodes could be among the driver of the early-type galaxy secular evolution. We present far and ... More
Probing the Emission Mechanism and Magnetic Field of Neutrino Blazars with Multi-Wavelength Polarization SignaturesMar 05 2019The characteristic two-component blazar spectral energy distribution (SED) can be of either leptonic and/or hadronic origins. The potential association of the high-energy neutrino event IceCube-170922A with the flaring blazar TXS~0506+056 indicates that ... More
Central UV Spikes in two Galactic SpheroidsJan 27 1999FOS spectra and FOC photometry of two centrally located, UV-bright spikes in the elliptical galaxy NGC 4552 and the bulge-dominated early spiral NGC 2681, are presented. These spectra reveal that such point-like UV sources detected by means of HST within ... More
Is the Giant Elliptical Galaxy NGC5018 a Post-Merger Remnant?Jun 23 2004NGC5018, one of the weakest UV emitters among giant ellipticals (gE) observed with IUE, appears to consist of an optical stellar population very similar to that of the compact, dwarf elliptical M32, which is several magnitudes fainter in luminosity than ... More
Fermi-LAT Observations of 2014 May-July outburst from 3C 454.3Nov 07 2015A prominent outburst of the flat spectrum radio quasar 3C~454.3 was observed in June 2014 with the Fermi Large Area Telescope. This outburst was characterized by a three-stage light-curve pattern---plateau, flare and post-flare---that occurred from 2014 ... More
The UV view of multi spin galaxies: insight from SPH simulationsJan 17 2014The UV images of GALEX revealed that ~30% of Early Type Galaxies (ETG) show UV emission indicating a rejuvenation episode. In ETGs with multiple spin components this percentage increases at 50%. We present here the characteristics of this sample and our ... More
Tracing rejuvenation events in nearby S0 galaxiesMay 19 2011With the aim of characterizing rejuvenation processes in early-type galaxies, we analyzed five barred S0 galaxies showing prominent outer ring in ultraviolet (UV) imaging. We analyzed GALEX far- (FUV) and near- (NUV) UV and optical data using stellar ... More
The impact of encounters on the members of Local Group Analogs. A view from GALEXJan 21 2008The bright galaxy population of the Local Group Analog (LGA) LGG 225 has been imaged with the Galaxy Evolution Explorer (GALEX) through its Far- and Near-UV wavebands. A significant fraction of the group members appear to underwent recent/on-going interaction ... More
UV Imaging of the Galaxy Cluster CL0939+4713 (Abell 851) at z=0.41Oct 05 1999The first UV F300W and F218W WFPC2 observations of the rich galaxy cluster CL0939+4713 at z=0.41 are presented and discussed. UV/optical two-color and c-m diagrams of the sources detected in the F300W waveband are constructed. Thanks to pre-existing HST ... More
NGC 7679: an anomalous, composite Seyfert 1 galaxy whose, X-ray luminous AGN vanishes at optical wavelengthsOct 03 2005Morphological disturbances and gas kinematics of the SB0 galaxy NGC 7679=Arp 216 are investigated to get clues to the history of this highly composite object, where AGN and starburst signatures dominate each other in the X-ray and optical/IR regime, respectively. ... More
Galaxy Evolution in Local Group Analogs. I. A GALEX study of nearby groupsDec 21 2009Understanding the astrophysical processes acting within galaxy groups and their effects on the evolution of the galaxy population is one of the crucial topic of modern cosmology, as almost 60% of galaxies in the Local Universe are found in groups. We ... More
Dating the formation of the counter-rotating stellar disc in the spiral galaxy NGC 5719 by disentangling its stellar populationsJan 16 2011Jan 18 2011We present the results of the VLT/VIMOS integral-field spectroscopic observations of the inner 28"x28" (3.1 kpc x 3.1 kpc) of the interacting spiral NGC 5719, which is known to host two co-spatial counter-rotating stellar discs. At each position in the ... More
Spectroscopic evidence of distinct stellar populations in the counter-rotating stellar disks of NGC 3593 and NGC 4550Oct 29 2012We present the results of integral-field spectroscopic observations of the two disk galaxies NGC 3593 and NGC 4550 obtained with VIMOS/VLT. Both galaxies are known to host 2 counter-rotating stellar disks, with the ionized gas co-rotating with one of ... More
The Cuspy LINER Nucleus of the S0/a Galaxy NGC 2681Dec 20 2000The nucleus of the bulge-dominated, multiply-barred S0/a galaxy NGC 2681 is studied in detail, using high resolution Hubble Space Telescope FOC and NICMOS imaging and FOS spectroscopy. The ionised gas central velocity dispersion is found to increase by ... More
Objects in NGC 205 Resolved into Stellar Associations by HST Ultraviolet ImagingJan 07 1999We have obtained high resolution UV images with the HST+WFPC2 of the central region of the dwarf elliptical galaxy NGC 205. Our images reveal that many of the hot UV stars previously detected and studied from the ground are actually multiple systems, ... More
Dissecting Kinematics and Stellar Populations of Counter-Rotating Galaxies with 2-Dimensional SpectroscopyFeb 21 2014We present a spectral decomposition technique and its applications to a sample of galaxies hosting large-scale counter-rotating stellar disks. Our spectral decomposition technique allows to separate and measure the kinematics and the properties of the ... More
Tracing the evolution of nearby early-type galaxies in low density environments. The Ultraviolet view from GALEXJan 05 2011We detected recent star formation in nearby early-type galaxies located in low density environments, with GALEX Ultraviolet (UV) imaging. Signatures of star formation may be present in the nucleus and in outer rings/arm like structures. Our study suggests ... More
A Unique Messenger to Probe Active Galactic Nuclei: High-Energy NeutrinosMar 11 2019This Astro2020 white paper advocates for a multi-messenger approach that combines high-energy neutrino and broad multi-wavelength electromagnetic observations to study AGN during the coming decade. The unique capabilities of these joint observations promise ... More
The ultraviolet flare at the center of the elliptical galaxy NGC 4278Sep 22 2009A large fraction of otherwise normal galaxies shows a weak nuclear activity. One of the signatures of the low-luminosity active galactic nuclei (LLAGNs) is the ultraviolet variability which was serendipitously discovered in the center of some low-ionization ... More
The Mini AGN at the Center of the Elliptical Galaxy NGC 4552 with HSTJul 07 1998Feb 12 1999The complex phenomenology shown by the UV-bright, variable spike first detected with the Hubble Space Telescope (HST) at the center of the otherwise normal galaxy NGC 4552 is further investigated with both HST imaging (FOC) and spectroscopy (FOS). HST/FOC ... More
The GALEX UV emission in shell galaxies: tracing galaxy "rejuvenation" episodesJul 19 2007We present the GALEX far FUV and near NUV ultraviolet imaging of three nearby shell galaxies, namely NGC 2865, NGC 5018 and NGC 7135. The system of shells and fine structures visible in the optical is detected in the NUV image of NGC 2865 and in both ... More
NGC5719/13: interacting spirals forming a counter-rotating stellar discNov 14 2006(Context) When a galaxy acquires material from the outside, it is likely that the resulting angular momentum of the accreted material is decoupled from that of the pre-existing galaxy. The presence of stars counter-rotating with respect to other stars ... More
The TANAMI Multiwavelength Program: Dynamic SEDs of Southern BlazarsMay 03 2016Simultaneous broadband spectral and temporal studies of blazars are an important tool for investigating active galactic nuclei (AGN) jet physics. We study the spectral evolution between quiescent and flaring periods of 22 radio-loud AGN through multi-epoch, ... More
Rapid Variability of Blazar 3C 279 during Flaring States in 2013-2014 with Joint Fermi-LAT, NuSTAR, Swift, and Ground-Based Multi-wavelength ObservationsFeb 16 2015Apr 02 2015We report the results of a multi-band observing campaign on the famous blazar 3C 279 conducted during a phase of increased activity from 2013 December to 2014 April, including first observations of it with NuSTAR. The $\gamma$-ray emission of the source ... More
Galaxy evolution in nearby groups. II. Galaxy evolution in nearby loose groups. II. Photometric and kinematic characterization of USGC U268 and USGC U376 group members in the Leo cloudSep 19 2012We present the photometric and kinematic characterization of two groups, USGC U268 and USGC U376 located in different regions of the Leo cloud. U268, composed of 10 catalogued members and 11 new added members, has a small fraction (~24%) of early-type ... More
GALEX UV properties of the polar ring galaxy MCG-05-07-001 and the shell galaxies NGC 1210 and NGC 5329Sep 22 2009Dec 21 2009Systems of shells and polar rings in early-type galaxies are considered "bona fide" tracers of mass accretion and/or mergers. Their high frequency in low density environments suggests that such episodes could drive the evolution of at least a fraction ... More
Multiband variability studies and novel broadband SED modeling of Mrk 501 in 2009Dec 30 2016We present an extensive study of the BL Lac object Mrk 501 based on a data set collected during the multi-instrument campaign spanning from 2009 March 15 to 2009 August 1 which includes, among other instruments, MAGIC, VERITAS, Whipple 10-m, Fermi-LAT, ... More
Early-type galaxies in the near-infrared: 1.5-2.4\mum spectroscopyAug 26 2008Near-infrared (hereafter NIR) data may provide complementary information to the traditional optical population synthesis analysis of unresolved stellar populations because the spectral energy distribution of the galaxies in the 1-2.5\mum range is dominated ... More
The Spectral Energy Distribution of Fermi bright blazarsDec 10 2009(Abridged) We have conducted a detailed investigation of the broad-band spectral properties of the \gamma-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated Fermi gamma-ray spectra with Swift, radio, ... More
Unresolved Gamma-Ray Sky through its Angular Power SpectrumDec 05 2018Dec 17 2018The gamma-ray sky has been observed with unprecedented accuracy in the last decade by the Fermi large area telescope (LAT), allowing us to resolve and understand the high-energy Universe. The nature of the remaining unresolved emission (unresolved gamma-ray ... More
Band insulator to Mott insulator transition in a bilayer Hubbard modelMar 27 2007The ground state phase diagram of the half-filled repulsive Hubbard model in a bilayer is investigated using cluster dynamical mean field theory. For weak to intermediate values of Coulomb repulsion $U$, the system undergoes a transition from a Mott insulating ... More
Search for Early Gamma-ray Production in Supernovae Located in a Dense Circumstellar Medium with the Fermi LATJun 04 2015Jun 26 2015Supernovae (SNe) exploding in a dense circumstellar medium (CSM) are hypothesized to accelerate cosmic rays in collisionless shocks and emit GeV gamma rays and TeV neutrinos on a time scale of several months. We perform the first systematic search for ... More
Constraints on the Galactic Halo Dark Matter from Fermi-LAT Diffuse MeasurementsMay 29 2012Jan 14 2013We have performed an analysis of the diffuse gamma-ray emission with the Fermi Large Area Telescope in the Milky Way Halo region searching for a signal from dark matter annihilation or decay. In the absence of a robust dark matter signal, constraints ... More
The second catalog of flaring gamma-ray sources from the Fermi All-sky Variability AnalysisDec 09 2016Sep 12 2017We present the second catalog of flaring gamma-ray sources (2FAV) detected with the Fermi All-sky Variability Analysis (FAVA), a tool that blindly searches for transients over the entire sky observed by the Large Area Telescope (LAT) on board the \textit{Fermi} ... More
Searching the Gamma-ray Sky for Counterparts to Gravitational Wave Sources: Fermi GBM and LAT Observations of LVT151012 and GW151226Jun 15 2016We present the Fermi Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) observations of the LIGO binary black hole merger event GW151226 and candi- date LVT151012. No candidate electromagnetic counterparts were detected by either the GBM or ... More
Modelling the VHE flare of 3C 279 using one zone leptonic modelSep 12 2011We model the simultaneous observations of the flat spectrum radio quasar 3C 279 at radio, optical, X-ray and very high energy (VHE) gamma ray energies during 2006 flare using a simple one zone leptonic model. We consider synchrotron emission due to cooling ... More
What Is Boolean Valued Analysis?Oct 05 2006May 08 2009This is a brief overview of the basic techniques of Boolean valued analysis.
Expected Number of Slope Crossings of Certain Gaussian Random PolynomialsDec 31 2006Let $Q_n(x)=\sum_{i=0}^{n} A_{i}x^{i}$ be a random polynomial where the coefficients $A_0,A_1,... $ form a sequence of centered Gaussian random variables. Moreover, assume that the increments $\Delta_j=A_j-A_{j-1}$, $j=0,1,2,...$ are independent, assuming ... More
On the Average Number of Sharp Crossings of Certain Gaussian Random PolynomialsMay 27 2006Let $Q_n(x)=\sum_{i=0}^{n} A_{i}x^{i}$ be a random algebraic polynomial where the coefficients $A_0,A_1,... $ form a sequence of centered Gaussian random variables. Moreover, assume that the increments $\Delta_j=A_j-A_{j-1}$, $j=0,1,2,...$ are independent, ... More
An iterated sum formula for a spheroid's homotopy class modulo 2-torsionJun 21 2006Let $X$ be a simply connected pointed space with finitely generated homotopy groups. Let $\Pi_n(X)$ denote the set of all continuous maps $a:I^n\to X$ taking $\partial I^n$ to the basepoint. For $a\in\Pi_n(X)$, let $[a]\in\pi_n(X)$ be its homotopy class. ... More
Technological Strategy of Using Global Positioning System: An AnalysisJan 23 2010The Global Positioning System (GPS) is a U.S. space-based radionavigation system that provides reliable positioning, navigation, and timing services to civilian users on a continuous worldwide basis -- freely available to all. GPS provides specially coded ... More
Resonating valence bond wave function for the two dimensional fractional spin liquidAug 13 2003Feb 19 2004The unconventional low-lying spin excitations, recently observed in neutron scattering experiments on ${\rm Cs_2 Cu Cl_4}$, are explained with a spin liquid wave function. The dispersion relation as well as the wave vector of the incommensurate spin correlations ... More
Enhanced signal propagation in a network with unidirectional and random couplingsApr 22 2014We investigate the effect of unidirectional regular and random couplings of units in a network on stochastic resonance. For simplicity we choose the units as Bellows map with bistability. In a regular network we apply a weak periodic signal and noise ... More
On $T$-sequences and characterized subgroupsFeb 04 2009Mar 08 2009Let $X$ be a compact metrizable abelian group and $\mathbf{u}=\{u_n\}$ be a sequence in its dual $X^{\wedge}$. Set $s_{\mathbf{u}} (X)= \{x: (u_n,x)\to 1\}$ and $\mathbb{T}_0^H = \{(z_n)\in \mathbb{T}^{\infty} : z_n\to 1 \}$. Let $G$ be a subgroup of ... More
On the Ascoli property for locally convex spaces and topological groupsNov 09 2016We characterize Ascoli spaces by showing that a Tychonoff space $X$ is Ascoli iff the canonical map from the free locally convex space $L(X)$ over $X$ into $C_k\big( C_k(X)\big)$ is an embedding of locally convex spaces. We prove that an uncountable direct ... More
Quotient Equations and Integrals of Motion for Massive Spinor FieldMar 29 2003In this article a group-theoretical aspect of the method of dimensional reduction is presented. Then, on the base of symmetry analysis of an anisotropic space geometrical description of dimensional reduction of equation for massive spinor field is given. ... More
Soft wall model with inverse exponential profile as a model for the axial and pseudoscalar mesonsJul 11 2012According to the conjecture of the gauge/gravity duality a strongly coupled 4D field theory may be described by a dual 5D theory which is a free field theory in the first approximation. The usual description of the axial-vector sector in the bottom-up ... More
No-Wall Holographic Model for QCDDec 22 2010Mar 03 2011We propose a new type of bottom-up holographic model describing the Regge like spectrum of mesons. This type of spectrum emerges due to condensation of a scalar field in the bulk anti-de Sitter space. The gauge invariance of the action describing the ... More
Holographic like models as a five-dimensional rewriting of large-Nc QCDJan 18 2010Oct 13 2010The AdS/QCD models are known to be tightly related with the QCD sum rules in the large-Nc (called also planar) limit. Rewriting the theory of infinite tower of free stable mesons expected in the large-Nc QCD as a five-dimensional theory we scrutinize ... More