Results for "S. Gezari"

total 155346took 0.18s
Follow-Up Chandra Observations of Three Candidate Tidal Disruption EventsFeb 20 2004Large-amplitude, high-luminosity soft X-ray flares were detected by the ROSAT All-Sky Survey in several galaxies with no evidence of Seyfert activity in their ground-based optical spectra. These flares had the properties predicted for a tidal disruption ... More
Long-Term Profile Variability of Double Peaked Emission Lines in Active Galactic NucleiFeb 21 2007We present up to two decades of spectroscopic monitoring of the double-peaked broad Halpha emission lines of seven broad-line radio galaxies. These extremely broad, double-peaked lines are successfully modeled by emission from gas in the outer accretion ... More
Probing Quiescent Massive Black Holes: Insights from Tidal Disruption EventsMar 05 2009Tidal disruption events provide a unique probe of quiescent black holes in the nuclei of distant galaxies. The next generation of synoptic surveys will yield a large sample of flares from the tidal disruption of stars by massive black holes that will ... More
Discovery of the Ultra-Bright Type II-L Supernova 2008esAug 21 2008Nov 18 2008We report the discovery by the Robotic Optical Transient Experiment (ROTSE-IIIb) telescope of SN 2008es, an overluminous supernova (SN) at z=0.205 with a peak visual magnitude of -22.2. We present multiwavelength follow-up observations with the Swift ... More
Probing Shock Breakout with Serendipitous GALEX Detections of Two SNLS Type II-P SupernovaeApr 07 2008Jul 31 2008We report the serendipitous detection by GALEX of fast (<1 day) rising (>1 mag) UV emission from two Type II plateau (II-P) supernovae (SNe) at z=0.185 and 0.324 discovered by the Supernova Legacy Survey. Optical photometry and VLT spectroscopy 2 weeks ... More
Adaptive Optics Near-Infrared Spectroscopy of the Sgr A* ClusterMay 13 2002We present K-band $\lambda/\Delta\lambda$ ~ 2600 spectroscopy of five stars (K ~ 14 - 16 mag) within 0.''5 of Sgr A*, the radio source associated with the compact massive object suspected to be a 2.6 x 10$^{6}$ \msun black hole at the center of our Galaxy. ... More
Follow-Up HST/STIS Spectroscopy of Three Candidate Tidal Disruption EventsApr 02 2003Large amplitude, high luminosity soft X-ray flares were detected by the ROSAT All-Sky Survey in several galaxies with no evidence for Seyfert activity in their ground-based optical spectra. These flares had the properties predicted for a tidal disruption ... More
H2O Masers and Supersonic TurbulenceOct 15 2002We use unpublished and published VLBI results to investigate the geometry and the statistical properties of the velocity field traced by H2O masers in five galactic regions of star formation -- Sgr B2(M), W49N, W51(MAIN), W51N, and W3(OH). In all sources ... More
A New Class of Changing-Look LINERsApr 24 2019We report the discovery of six active galactic nuclei (AGN) caught "turning on" during the first nine months of the Zwicky Transient Facility (ZTF) survey. The host galaxies were classified as LINERs by weak narrow forbidden line emission in their archival ... More
An Arena for Multi-Messenger Astrophysics: Inspiral and Tidal Disruption of White Dwarfs by Massive Black HolesFeb 18 2019The tidal disruption of stars by (super-)massive black holes in galactic nuclei has been discussed in theoretical terms for about 30 years but only in the past decade have we been able to detect such events in substantial numbers. Thus, we are now starting ... More
PS1-10jh Continues to Follow the Fallback Accretion Rate of a Tidally Disrupted StarNov 19 2015We present late-time observations of the tidal disruption event candidate PS1-10jh. UV and optical imaging with HST/WFC3 localize the transient to be coincident with the host galaxy nucleus to an accuracy of 0.023 arcsec, corresponding to 66 pc. The UV ... More
Late-time UV observations of tidal disruption flares reveal unobscured, compact accretion disksAug 31 2018The origin of thermal optical and UV emission from stellar tidal disruption flares (TDFs) remains an open question. We present Hubble Space Telescope far-UV (FUV) observations of eight optical/UV selected TDFs 5-10 years post-peak. Six sources are cleanly ... More
The host galaxy properties of variability selected AGN in the Pan-STARRS1 Medium-Deep SurveyMay 07 2016We study the properties of 975 active galactic nuclei (AGN) selected by variability in the Pan-STARRS1 Medium-Deep Survey. Using complementary multi wavelength data from the ultraviolet to the far-infrared, we use SED fitting to determine the AGN and ... More
Of Genes and Machines: application of a combination of machine learning tools to astronomy datasetsMar 03 2016We apply a combination of a Genetic Algorithms (GA) and Support Vector Machines (SVM) machine learning algorithm to solve two important problems faced by the astronomical community: star/galaxy separation, and photometric redshift estimation of galaxies ... More
Black hole masses of tidal disruption event host galaxies IIFeb 11 2019We present new medium resolution, optical long-slit spectra of a sample of 6 UV/optical and 15 X-ray selected tidal disruption event candidate host galaxies. We measure emission line ratios from the optical spectra, finding that the large majority of ... More
The Mid-Infrared Colors of the ISM and Extended Sources at the Galactic CenterApr 28 2008A mid-infrared (3.6-8 um) survey of the Galactic Center has been carried out with the IRAC instrument on the Spitzer Space Telescope. This survey covers the central 2x1.4 degree (~280x200 pc) of the Galaxy. At 3.6 and 4.5 um the emission is dominated ... More
A Systematic Search for Periodically Varying Quasars in Pan-STARRS1: An Extended Baseline Test in Medium Deep Survey Field MD09Sep 29 2016Nov 14 2016We present a systematic search for periodically varying quasars and supermassive black hole binary (SMBHB) candidates in the Pan-STARRS1 (PS1) Medium Deep Survey's MD09 field. From a color-selected sample of 670 quasars extracted from a multi-band deep-stack ... More
A Systematic Search for Periodically Varying Quasars in Pan-STARRS1: An Extended Baseline Test in Medium Deep Survey Field MD09Sep 29 2016We present a systematic search for periodically varying quasars and supermassive black hole binary (SMBHB) candidates in the Pan-STARRS1 (PS1) Medium Deep Survey's MD09 field. From a color-selected sample of 670 quasars extracted from a multi-band deep-stack ... More
The first tidal disruption flare in ZTF: from photometric selection to multi-wavelength characterizationSep 07 2018Feb 07 2019We present Zwicky Transient Facility (ZTF) observations of the tidal disruption flare AT2018zr/PS18kh reported by Holoien et al. and detected during ZTF commissioning. The ZTF light curve of the tidal disruption event (TDE) samples the rise-to-peak exceptionally ... More
Did ASAS-SN Kill the Supermassive Black Hole Binary Candidate PG1302-102?Mar 14 2018May 11 2018Graham et al. (2015a) reported a periodically varying quasar and supermassive black hole binary candidate, PG1302-102 (hereafter PG1302), which was discovered in the Catalina Real-Time Transient Survey (CRTS). Its combined Lincoln Near-Earth Asteroid ... More
UV/Optical Detections of Candidate Tidal Disruption Events by GALEX and CFHTLSDec 26 2007Feb 20 2008We present two luminous UV/optical flares from the nuclei of apparently inactive early-type galaxies at z=0.37 and 0.33 that have the radiative properties of a flare from the tidal disruption of a star. In this paper we report the second candidate tidal ... More
Comparison of 3.6 - 8.0 Micron Spitzer/IRAC Galactic Center Survey Point Sources with Chandra X-Ray Point Sources in the Central 40x40 ParsecsJun 11 2008We have studied the correlation between 2357 Chandra X-ray point sources in a 40 x 40 parsec field and ~20,000 infrared sources we observed in the corresponding subset of our 2 x 1.4 degree Spitzer/IRAC Galactic Center Survey at 3.6-8.0 um, using various ... More
Revisiting optical tidal disruption events with iPTF16axaMar 03 2017May 15 2017We report the discovery by the intermediate Palomar Transient Factory (iPTF) of a candidate tidal disruption event (TDE) iPTF16axa at $z=0.108$, and present its broadband photometric and spectroscopic evolution from 3 months of follow-up observations ... More
The Fast, Luminous Ultraviolet Transient AT2018cow: Extreme Supernova, or Disruption of a Star by an Intermediate-Mass Black Hole?Aug 02 2018Nov 23 2018Wide-field optical surveys have begun to uncover large samples of fast (t_rise < 5d), luminous (M_peak < -18), blue transients. While commonly attributed to the breakout of a supernova shock into a dense wind, the great distances to the transients of ... More
Luminous Thermal Flares from Quiescent Supermassive Black HolesApr 09 2009Apr 29 2009A dormant supermassive black hole lurking in the center of a galaxy will be revealed when a star passes close enough to be torn apart by tidal forces, and a flare of electromagnetic radiation is emitted when the bound fraction of the stellar debris falls ... More
Spectral analysis of four 'hypervariable' AGN: a micro-needle in the haystack?Aug 22 2016We analyze four extreme AGN transients to explore the possibility that they are caused by rare, high-amplitude microlensing events. These previously unknown type-I AGN are located in the redshift range 0.6-1.1 and show changes of > 1.5 magnitudes in the ... More
Spectral analysis of four 'hypervariable' AGN: a microneedle in the haystack?Aug 22 2016Mar 03 2017We analyze four extreme active galactic nuclei (AGN) transients to explore the possibility that they are caused by rare, high-amplitude microlensing events. These previously unknown type-I AGN are located in the redshift range 0.6-1.1 and show changes ... More
Ultraviolet Detection of the Tidal Disruption of a Star by a Supermassive Black HoleDec 04 2006A supermassive black hole in the nucleus of a galaxy will be revealed when a star passes close enough to be torn apart by tidal forces and a flare of radiation is emitted by the stream of stellar debris that plunges into the black hole. Since common active ... More
A Periodically Varying Luminous Quasar at z=2 from the Pan-STARRS1 Medium Deep Survey: A Candidate Supermassive Black Hole Binary in the Gravitational Wave-Driven RegimeMar 06 2015May 21 2015Supermassive black hole binaries (SMBHBs) should be an inevitable consequence of the hierarchical growth of massive galaxies through mergers, and the strongest sirens of gravitational waves (GWs) in the cosmos. And yet, their direct detection has remained ... More
The GALEX Time Domain Survey. II. Wavelength-Dependent Variability of Active Galactic Nuclei in the Pan-STARRS1 Medium Deep SurveySep 20 2016We analyze the wavelength-dependent variability of a sample of spectroscopically confirmed active galactic nuclei (AGN) selected from near-UV ($NUV$) variable sources in the GALEX Time Domain Survey that have a large amplitude of optical variability (difference-flux ... More
The GALEX Time Domain Survey I. Selection and Classification of Over a Thousand UV Variable SourcesFeb 06 2013We present the selection and classification of over a thousand ultraviolet (UV) variable sources discovered in ~ 40 deg^2 of GALEX Time Domain Survey (TDS) NUV images observed with a cadence of 2 days and a baseline of observations of ~ 3 years. The GALEX ... More
Sifting for Sapphires: Systematic Selection of Tidal Disruption Events in iPTFDec 13 2017Aug 13 2018We present results from a systematic selection of tidal disruption events (TDEs) in a wide-area (4800~deg$^2$), $g+R$ band, Intermediate Palomar Transient Factory (iPTF) experiment. Our selection targets typical optically-selected TDEs: bright ($>$60\% ... More
The growth and evolution of super massive black holesMar 30 2009We discuss the central role played by X-ray studies to reconstruct the past history of formation and evolution of supermassive Black Holes (BHs), and the role they played in shaping the properties of their host galaxies. We shortly review the progress ... More
Probing the Invisible Universe: The Case for Far-IR/Submillimeter InterferometryFeb 04 2002The question "How did we get here and what will the future bring?" captures the human imagination and the attention of the National Academy of Science's Astronomy and Astrophysics Survey Commitee (AASC). Fulfillment of this "fundamental goal" requires ... More
iPTF Discovery of the Rapid "Turn On" of a Luminous QuasarDec 14 2016We present a radio-quiet quasar at z=0.237 discovered "turning on" by the intermediate Palomar Transient Factory (iPTF). The transient, iPTF 16bco, was detected by iPTF in the nucleus of a galaxy with an archival SDSS spectrum with weak narrow-line emission ... More
Slow blue nuclear hypervariables in PanSTARRS-1May 25 2016Aug 05 2016We discuss 76 large amplitude transients (Delta-m>1.5) occurring in the nuclei of galaxies, nearly all with no previously known Active Galactic Nucleus (AGN). They have been discovered as part of the Pan-STARRS1 (PS1) 3pi survey, by comparison with SDSS ... More
The Extra-Solar Planet Imager (ESPI)Oct 02 2002ESPI has been proposed for direct imaging and spectral analysis of giant planets orbiting solar-type stars. ESPI extends the concept suggested by Nisenson and Papaliolios (2001) for a square aperture apodized telescope that has sufficient dynamic range ... More
An Ultraviolet Spectrum of the Tidal Disruption Flare ASASSN-14liJan 13 2016Feb 02 2016We present a Hubble Space Telescope STIS spectrum of ASASSN-14li, the first rest-frame UV spectrum of a tidal disruption flare (TDF). The underlying continuum is well fit by a blackbody with $T_{\mathrm{UV}} = 3.5 \times 10^{4}$ K, an order of magnitude ... More
Flows of X-ray gas reveal the disruption of a star by a massive black holeOct 21 2015Tidal forces close to massive black holes can violently disrupt stars that make a close approach. These extreme events are discovered via bright X-ray and optical/UV flares in galactic centers. Prior studies based on modeling decaying flux trends have ... More
The detection rate of early UV emission from supernovae: A dedicated GALEX/PTF survey and calibrated theoretical estimatesDec 12 2014Feb 25 2015The radius and surface composition of an exploding massive star,as well as the explosion energy per unit mass, can be measured using early UV observations of core collapse supernovae (SNe). We present the first results from a simultaneous GALEX/PTF search ... More
Selection of Burst-like Transients and Stochastic Variables Using Multi-Band Image Differencing in the Pan-STARRS1 Medium-Deep SurveyJan 06 2015We present a novel method for the light-curve characterization of Pan-STARRS1 Medium Deep Survey (PS1 MDS) extragalactic sources into stochastic variables (SV) and burst-like (BL) transients, using multi-band image-differencing time-series data. We select ... More
Towards Characterization of the Type IIP Supernova Progenitor Population: a Statistical Sample of Light Curves from Pan-STARRS1Apr 08 2014Feb 01 2015In recent years, wide-field sky surveys providing deep multi-band imaging have presented a new path for indirectly characterizing the progenitor populations of core-collapse supernovae (SN): systematic light curve studies. We assemble a set of 76 grizy-band ... More
The Discovery and Nature of Optical Transient CSS100217:102913+404220Mar 29 2011We report on the discovery and observations of the extremely luminous optical transient CSS100217:102913+404220 (CSS100217 hereafter). Spectroscopic observations show this transient was coincident with a galaxy at redshift z=0.147, and reached an apparent ... More
Active Galaxy Science in the LSST Deep-Drilling Fields: Footprints, Cadence Requirements, and Total-Depth RequirementsNov 15 2018Nov 21 2018This white paper specifies the footprints, cadence requirements, and total-depth requirements needed to allow the most-successful AGN studies in the four currently selected LSST Deep-Drilling Fields (DDFs): ELAIS-S1, XMM-LSS, CDF-S, and COSMOS. The information ... More
Discovery of Highly Blueshifted Broad Balmer and Metastable Helium Absorption Lines in a Tidal Disruption EventMar 13 2019We report the discovery of non-stellar hydrogen Balmer and metastable helium absorption lines accompanying a transient, high-velocity (0.05$c$) broad absorption line (BAL) system in the optical spectra of the tidal disruption event (TDE) AT2018zr ($z=0.071$). ... More
The Zwicky Transient Facility: System Overview, Performance, and First ResultsFeb 05 2019The Zwicky Transient Facility (ZTF) is a new optical time-domain survey that uses the Palomar 48-inch Schmidt telescope. A custom-built wide-field camera provides a 47 deg$^2$ field of view and 8 second readout time, yielding more than an order of magnitude ... More
iPTF Survey for Cool TransientsNov 28 2017Jan 12 2018We performed a wide-area (2000 deg$^{2}$) g and I band experiment as part of a two month extension to the Intermediate Palomar Transient Factory. We discovered 36 extragalactic transients including iPTF17lf, a highly reddened local SN Ia, iPTF17bkj, a ... More
GALEX Detection of Shock Breakout in Type II-P Supernova PS1-13arp: Implications for the Progenitor Star WindFeb 24 2015We present the GALEX detection of a UV burst at the time of explosion of an optically normal Type II-P supernova (PS1-13arp) from the Pan-STARRS1 survey at z=0.1665. The temperature and luminosity of the UV burst match the theoretical predictions for ... More
The Zwicky Transient Facility: Science ObjectivesFeb 05 2019The Zwicky Transient Facility (ZTF), a public-private enterprise, is a new time domain survey employing a dedicated camera on the Palomar 48-inch Schmidt telescope with a 47 deg$^2$ field of view and 8 second readout time. It is well positioned in the ... More
A Multi-wavelength Analysis of Binary-AGN Candidate PSO J334.2028+01.4075Nov 15 2017We present analysis of the first Chandra observation of PSO J334.2028+01.4075 (PSO J334), targeted as a binary-AGN candidate based on periodic variations of the optical flux. With no prior targeted X-ray coverage for PSO J334, our new 40 ksec Chandra ... More
Multi-Messenger Astrophysics: Harnessing the Data RevolutionJul 12 2018The past year has witnessed discovery of the first identified counterparts to a gravitational wave transient (GW 170817A) and a very high-energy neutrino (IceCube-170922A). These source identifications, and ensuing detailed studies, have realized longstanding ... More
A Smart and Colorful Cadence for the LSST Wide Fast Deep Survey: Maximizing TDE ScienceDec 17 2018Tidal disruption events (TDEs) are rare, 10^(-7)/yr/Mpc^3 (Hung et al. 2018), yet the large survey volume of LSST implies a very large detection rate of 200/yr/(1000 deg^2) (van Velzen et al. 2011), a factor of 250 increase in the detection capability ... More
SN 1994W: An Interacting Supernova or Two Interacting Shells?Apr 02 2008Oct 06 2008We present a multi-epoch quantitative spectroscopic analysis of the Type IIn SN 1994W, an event interpreted by Chugai et al. as stemming from the interaction between the ejecta of a SN and a 0.4Msun circumstellar shell ejected 1.5yr before core collapse. ... More
SDSSJ092712.65+294344.0: NGC 1275 at z=0.7?Oct 07 2008Dec 04 2008SDSSJ092712.65+294344.0 was identified by the SDSS as a quasar, but has the unusual property of having two emission line systems offset by 2650 km/s. One of these contains the usual combination of broad and narrow lines, the other only narrow lines. In ... More
Revealing the Nature of Extreme Coronal-line Emitter SDSS J095209.56+214313.3Dec 29 2015Extreme coronal-line emitter (ECLE) SDSSJ095209.56+214313.3, known by its strong, fading, high ionization lines, has been a long standing candidate for a tidal disruption event, however a supernova origin has not yet been ruled out. Here we add several ... More
The mean infrared emission of SagittariusA*Jun 28 2011(abridged) The massive black hole at the center of the Milky Way, SagittariusA* is, in relative terms, the weakest accreting black hole accessible to observations. At the moment, the mean SED of SgrA* is only known reliably in the radio to mm regimes. ... More
Pan-STARRS1 Discovery of Two Ultra-Luminous Supernovae at z ~ 0.9Jul 18 2011Sep 06 2011We present the discovery of two ultra-luminous supernovae (SNe) at z ~ 0.9 with the Pan-STARRS1 Medium-Deep Survey. These SNe, PS1-10ky and PS1-10awh, are amongst the most luminous SNe ever discovered, comparable to the unusual transients SN 2005ap and ... More
Ultra-bright optical transients are linked with type Ic supernovaeAug 16 2010Sep 09 2010Recent searches by unbiased, wide-field surveys have uncovered a group of extremely luminous optical transients. The initial discoveries of SN 2005ap by the Texas Supernova Search and SCP-06F6 in a deep Hubble pencil beam survey were followed by the Palomar ... More
Rapidly-Evolving and Luminous Transients from Pan-STARRS1May 14 2014Aug 07 2014In the past decade, several rapidly-evolving transients have been discovered whose timescales and luminosities are not easily explained by traditional supernovae (SN) models. The sample size of these objects has remained small due, at least in part, to ... More
GALEX and Pan-STARRS1 Discovery of SN IIP 2010aq: The First Few Days After Shock Breakout in a Red Supergiant StarJul 26 2010Aug 16 2010We present the early UV and optical light curve of Type IIP supernova (SN) 2010aq at z=0.0862, and compare it to analytical models for thermal emission following SN shock breakout in a red supergiant star. SN 2010aq was discovered in joint monitoring ... More
iPTF16fnl: a faint and fast tidal disruption event in an E+A galaxyMar 02 2017May 25 2017We present ground-based and \textit{Swift} observations of iPTF16fnl, a likely tidal disruption event (TDE) discovered by the intermediate Palomar Transient Factory (iPTF) survey at 66.6 Mpc. The lightcurve of the object peaked at absolute $M_g=-17.2$ ... More
Pushing the Boundaries of Conventional Core-Collapse Supernovae: The Extremely Energetic Supernova SN 2003maNov 10 2009Dec 21 2010We report the discovery of a supernova (SN) with the highest apparent energy output to date and conclude that it represents an extreme example of the Type IIn subclass. The SN, which was discovered behind the Large Magellanic Cloud at z = 0.289 by the ... More
Black hole masses of tidal disruption event host galaxiesJun 27 2017The mass of the central black hole in a galaxy that hosted a tidal disruption event (TDE) is an important parameter in understanding its energetics and dynamics. We present the first homogeneously measured black hole masses of a complete sample of 12 ... More
An ultraviolet-optical flare from the tidal disruption of a helium-rich stellar coreMay 01 2012The flare of radiation from the tidal disruption and accretion of a star can be used as a marker for supermassive black holes that otherwise lie dormant and undetected in the centres of distant galaxies. Previous candidate flares have had declining light ... More
High Angular Resolution Mid-infrared Imaging of Young Stars in Orion BN/KLFeb 18 2004We present Keck LWS images of the Orion BN/KL star forming region obtained in the first multi-wavelength study to have 0.3-0.5" resolution from 4.7 to 22 microns. The young stellar objects designated infrared source-n and radio source-I are believed to ... More
The UV-bright, Slowly Declining Transient PS1-11af as a Partial Tidal Disruption EventSep 12 2013We present the Pan-STARRS1 discovery of the long-lived and blue transient PS1-11af, which was also detected by GALEX with coordinated observations in the near-ultraviolet (NUV) band. PS1-11af is associated with the nucleus of an early-type galaxy at redshift ... More
The Dynamic X-ray Sky of the Local UniverseFeb 23 2009Over the next decade, we can expect time domain astronomy to flourish at optical and radio wavelengths. In parallel with these efforts, a dedicated transient "machine" operating at higher energies (X-ray band through soft gamma-rays) is required to reveal ... More
Slowly fading super-luminous supernovae that are not pair-instability explosionsOct 16 2013Oct 10 2016Super-luminous supernovae that radiate more than 10^44 ergs per second at their peak luminosity have recently been discovered in faint galaxies at redshifts of 0.1-4. Some evolve slowly, resembling models of 'pair-instability' supernovae. Such models ... More
SN 2009kf : a UV bright type IIP supernova discovered with Pan-STARRS 1 and GALEXJan 29 2010May 12 2010We present photometric and spectroscopic observations of a luminous type IIP Supernova 2009kf discovered by the Pan-STARRS 1 (PS1) survey and detected also by GALEX. The SN shows a plateau in its optical and bolometric light curves, lasting approximately ... More
Optical discovery of probable stellar tidal disruption flaresSep 08 2010Sep 13 2011Using archival SDSS multi-epoch imaging data (Stripe 82), we have searched for the tidal disruption of stars by super-massive black holes in non-active galaxies. Two candidate tidal disruption events (TDEs) are identified. They have optical black-body ... More
From Cosmic Birth to Living Earths: The Future of UVOIR Space AstronomyJul 16 2015Jul 28 2015For the first time in history, humans have reached the point where it is possible to construct a revolutionary space-based observatory that has the capability to find dozens of Earth-like worlds, and possibly some with signs of life. This same telescope, ... More
Big Science with a nUV-MidIR Rapid-Response 1.3m telescope at L2Mar 19 2019Time-domain Astrophysics (TDA), a foundation of Astronomy, has become a major part of current and projected (2020s) astrophysics. While much has been derived from temporal measures of flux and color, the real physics comes from spectroscopy. With LSST ... More
Kilonovae: nUV/Optical/IR Counterparts of Neutron Star Binary Mergers with TSOMar 13 2019With the epochal first detection of gravitational waves from a binary neutron star (NS) merger with the GW170817 event, and its direct confirmation that NS-NS mergers are significant sources of the of the r-process nucleosynthesis of heavy elements, an ... More
GRBs as Probes of the Early Universe with TSOMar 19 2019Long gamma-ray bursts (GRBs) are the most luminous known electromagnetic radiation sources in the Universe for the 3 to 300 sec of their prompt flashes (isotropic X/ gamma-ray luminosities up to 10^53 ergs/sec). Their afterglows have first day rest-frame ... More
The Pan-STARRS1 SurveysDec 16 2016Jan 29 2019Pan-STARRS1 has carried out a set of distinct synoptic imaging sky surveys including the $3\pi$ Steradian Survey and the Medium Deep Survey in 5 bands ($grizy_{P1}$). The mean 5$\sigma$ point source limiting sensitivities in the stacked 3$\pi$ Steradian ... More
NNLO classical solution for Lipatov's effective action for reggeized gluonsFeb 15 2018Mar 19 2018We consider the formalism of small-x effective action for reggeized gluons, Gribov (Sov Phys JETP 26:414, 1968), Lipatov (Nucl Phys B 452:369, 1995; Phys Rep 286:131, 1997; Subnucl Ser 49:131, 2013, Int J Mod Phys Conf Ser 39:1560082, 2015; Int J Mod ... More
Ghost-Stochastic Resonance in a Unidirectionally Coupled and Small-World NetworksOct 27 2015Ghost-stochastic resonance is a noise-induced resonance at a missing fundamental frequency in the input signal. In this paper we investigate the features of ghost-stochastic resonance in a unidirectionally coupled network and small-world network with ... More
Signal amplification by unidirectional coupling of oscillatorsApr 22 2014We report our investigation on the input signal amplification in unidirectionally coupled monostable Duffing oscillators in one- and two-dimensions with first oscillator alone driven by a weak periodic signal. Applying a perturbation theory we obtain ... More
Complex molecular gas structure in the Medusa mergerAug 16 2000High resolution OVRO aperture synthesis maps of the 12CO 1-0 emission in the `Medusa' galaxy merger (NGC4194) reveal the molecular emission being surprisingly extended. It is distributed on a total scale of 25$''$ (4.7 kpc) - despite the apparent advanced ... More
Direct evidence of soft mode behavior near the Burns' temperature in PbMg$_{1 / 3}$Nb$_{2 / 3}$O$_{3}$ (PMN) relaxor ferroectricMar 05 2002Inelastic neutron scattering measurements of the relaxor ferroelectric PbMg$_{1 / 3}$Nb$_{2 / 3}$O$_{3}$ (PMN) in the temperature range 490~K$<$T$<$880~K directly observe the soft mode (SM) associated with the Curie-Weiss behavior of the dielectric constant ... More
Pair production by a circularly polarized electromagnetic wave in plasmaJul 23 2003Mar 15 2004We present the results of the calculation of the electron-positron pair creation probability by the circularly polarized electromagnetic wave during its propagation in underdense collisionless plasmas. The dependence of the probability on the frequency ... More
How much information can be obtained by a quantum measurement?Jul 21 1999How much information about an unknown quantum state can be obtained by a measurement? We propose a model independent answer: the information obtained is equal to the minimum entropy of the outputs of the measurement, where the minimum is taken over all ... More
Review and Analysis of Local Multipoint Distribution System (LMDS) to Deliver Voice, Data, Internet, and Video ServicesJan 23 2010Local multipoint distribution system (LMDS) uses cellular-like network architecture of microwave radios placed at the client's location and at the company's base station to deliver fixed services, mainly telephony, video and Internet access. The use of ... More
Unitarity and the scale of fermion mass generationJun 05 1998Jun 30 1998We study the upper bound on the scale of fermion mass generation in a two-Higgs-doublet model. If the model is weakly-coupled, the scale of fermion mass generation is much less than the Appelquist-Chanowitz unitarity bound. However, if we allow some dimensionless ... More
Young star clusters in external galaxiesJul 20 2011I review the characteristics of cluster populations in other galaxies, with particular emphasis on young star clusters and a comparison with the (known) open cluster population of the Milky Way. Young globular cluster-like (compact, massive) objects can ... More
Young Massive Star Clusters in Normal GalaxiesMar 10 2004Young star clusters with masses similar to those of classical old globular clusters are observed not only in starbursts, mergers or otherwise disturbed galaxies, but also in normal spiral galaxies. Some young clusters with masses as high as ~10^6 Msun ... More
Nonlocal spin Hall effect and spin-orbit interaction in nonmagnetic metalsSep 08 2006Spin Hall effect in a nonlocal spin-injection device is theoretically studied. Using a nonlocal spin-injection technique, a pure spin current is created in a nonmagnetic metal (N). The spin current flowing in N is deflected by spin-orbit scattering to ... More
A Classical Fuzzy Approach for Software Effort Estimation on Machine Learning TechniqueDec 16 2011Software Cost Estimation with resounding reliability,productivity and development effort is a challenging and onerous task. This has incited the software community to give much needed thrust and delve into extensive research in software effort estimation ... More
An illustration of the light-front coupled-cluster method in quantum electrodynamicsAug 30 2012A field-theoretic formulation of the exponential-operator technique is applied to a nonperturbative Hamiltonian eigenvalue problem in electrodynamics, quantized in light-front coordinates. Specifically, we consider the dressed-electron state, without ... More
Non-Markovianity by Quantum LossJun 22 2014In the study of open quantum systems, information exchange between system and its surrounding environment plays an eminent and important role in analysing the dynamics of open quantum system. In this work, by making use of the quantum information theory ... More
The Batalin-Vilkovisky Formalism on Fermionic Kaehler ManifoldsMay 19 1993We show that the Kaehler structure can be naturally incorporated in the Batalin-Vilkovisky formalism. The phase space of the BV formalism becomes a fermionic Kaehler manifold. By introducing an isometry we explicitly construct the fermionic irreducible ... More
Symbiotic Miras vs. Planetary Nebulae in the Near InfraredAug 06 2002While symbiotic Miras and planetary nebulae are hard to distinguish by optical spectroscopy, their near infrared colors differ. We propose the near infrared two-color diagram to be an excellent tool to easily distinguish these two classes of objects.
Fundamental Physical Constants and the Principle of Parametric IncompletenessSep 07 1999The principle which allows to construct new physical theories on the basis of classical mechanics by reduction of the number of its axiom without engaging new postulates is formulated. The arising incompleteness of theory manifests itself in terms of ... More
Black holes may not constrain varying constantsSep 27 2002New and rather controversial observations hint that the fine structure constant \alpha may have been smaller in the early universe, suggesting that some of the fundamental ``constants'' of physics may be dynamical. In a recent paper, Davies, Davis, and ... More
Phase Transitions and Critical Behavior for Charged Black HolesJun 12 2003We investigate the thermodynamics of a four-dimensional charged black hole in a finite cavity in asymptotically flat and asymptotically de Sitter space. In each case, we find a Hawking-Page-like phase transition between a black hole and a thermal gas ... More
Signatures of polaronic charge ordering in optical and dc conductivity using dynamical mean field theoryFeb 28 2008Apr 29 2008We apply dynamical mean field theory to study a prototypical model that describes charge ordering in the presence of both electron-lattice interactions and intersite electrostatic repulsion between electrons. We calculate the optical and d.c. conductivity, ... More
Spectral properties and isotope effect in strongly interacting systems: Mott-Hubbard insulator and polaronic semiconductorMay 17 2005Jun 13 2005We study the electronic spectral properties in two examples of strongly interacting systems: a Mott-Hubbard insulator with additional electron-boson interactions, and a polaronic semiconductor. An approximate unified framework is developed for the high ... More
Heavy-quark deep-inelastic scattering with a running massNov 26 2010We study the production of heavy quarks in deep-inelastic scattering within perturbative QCD. As a novelty, we employ for the first time the running mass definition in the MSbar scheme for deep-inelastic charm and bottom production. We observe an improved ... More
Continuous and smooth envelopes of topological algebrasMar 11 2013Sep 28 2016Since the first optical instruments have been invented, an idea that the visible image of an object under observation depends on tools of observation became commonly assumed in physics. A way to formalize it in mathematics is the construction that assigns ... More
Gas Properties in the Starburst Centers of Barred GalaxiesJul 16 2001The physical properties of molecular gas can be deduced from the analysis of line intensity ratios, most commonly of the CO isotopomers 12CO and 13CO. Barred galaxies, especially those with central starbursts, provide an excellent laboratory to study ... More