Now showing items 800-819 of 841

    • Variability and Proper Motion of X-ray Knots in the Jet of Centaurus A 

      Snios, Bradford; Wykes, Sarka; Nulsen, Paul E. J.; Kraft, Ralph P.; Meyer, Eileen T.; Birkinshaw, Mark; Worrall, Diana M.; Hardcastle, Martin J.; Roediger, Elke; Forman, William R.; Jones, Christine (2019-01-22)
      We report results from Chandra observations analyzed for evidence of variability and proper motion in the X-ray jet of Centaurus A. Using data spanning 15 years, collective proper motion of 11.3±3.3 mas yr We report results ...
    • The variable and non-variable X-ray absorbers in Compton-thin type-II Active Galactic Nuclei 

      Laha, Sibasish; Markowitz, Alex G.; Krumpe, Mirko; Nikutta, Robert; Rothschild, Richard; Saha, Tathagata (2020-05-12)
      We have conducted an extensive X-ray spectral variability study of a sample of 20 Compton-thin type II galaxies using broad band spectra from XMM-Newton, Chandra, and Suzaku. The aim is to study the variability of the ...
    • Velocity-dependent optical forces and Maxwell’s demon 

      Franson, J. D. (Nature, 2019-09-24)
      An atom placed in a focused laser beam will experience a dipole force due to the gradient in the interaction energy, which is analogous to the well-known optical tweezers effect. This force will be dependent on the velocity ...
    • VERITAS and Fermi-LAT Observations of TeV Gamma-Ray Sources Discovered by HAWC in the 2HWC Catalog 

      Ojha, Roopesh; et al. (The American Astronomical Society, 2018-10-05)
      The High Altitude Water Cherenkov (HAWC) collaboration recently published their 2HWC catalog, listing 39 very high energy (VHE; >100 GeV) gamma-ray sources based on 507 days of observation. Among these, 19 sources are not ...
    • VERITAS Discovery of VHE Emission from the Radio Galaxy 3C 264: A Multi-Wavelength Study 

      A. Archer; et al (2020-05-06)
      The radio source 3C 264, hosted by the giant elliptical galaxy NGC 3862, was observed with VERITAS between February 2017 and May 2019. These deep observations resulted in the discovery of very-high-energy (VHE; E >100 GeV) ...
    • Vertical Dependence of Horizontal Variation of Cloud Microphysics: Observations from theACE-ENA field campaign and implications for warm rain simulation in climate models 

      Zhang, Zhibo; Song, Qianqian; Mechem, David; Larson, Vincent; Wang, Jian; Liu, Yangang; Witte, Mikael; Dong, Xiquan; Wu, Peng (Copernicus Publications, 2020-08-11)
      In the current global climate models (GCM), the nonlinearity effect of subgrid cloud variations on the parameterization of warm rain process, e.g., the autoconversion rate, is often treated by multiplying the resolved-scale ...

      Ojha, R.; Mirabal, N.; et al. (IOP, 2015-12-15)
      The flat-spectrum radio quasar PKS 1441+25 at a redshift of z = 0.940 is detected between 40 and 250 GeV with a significance of 25.5σ using the MAGIC telescopes. Together with the gravitationally lensed blazar QSO B0218+357 ...
    • Viewpoint: Equilibration in Quantum Systems 

      Deffner, Sebastian (American Physical Society, 2019-11-13)
      Two research groups show that specific contributions to entropy may be the key to understanding how and when quantum systems equilibrate.
    • Violating Bell’s inequality using a number state and a beam splitter 

      Shringarpure, S.U.; Franson, J.D. (2019-11-06)
      Passing a photon number state through a balanced beam splitter will produce an entangled state in which the phases of the two output modes are highly correlated. We show that Bell’s inequality can be violated using this ...
    • Violation of Bell’s Inequality with Photons from Independent Sources 

      Pittman, T.B.; Franson, J.D. (American Physical Society (APS), 2003-06-19)
      We report a violation of Bell’s inequality using one photon from a parametric down-conversion source and a second photon from an attenuated laser beam. The two photons were entangled at a beam splitter using the postselection ...
    • Virtual Telescope for X-ray Observations: VTXO 

      Krizmanic, John
      Precision formation flying of a OpticsSat with X-ray Phase Fresnel Lens (PFL) Optics and a DetectorSat with an X-ray camera forming a 1 km focal length X-ray telescope with 55 milli-arcsecond angular resolution and 8 arcsecond FoV
    • Visualizing Heterogeneity of Monodisperse CdSe Nanocrystals by Their Assembly into Three-Dimensional Supercrystals 

      Shevchenko, Elena V.; Podsiadlo, Paul; Wu, Xiaohua; Lee, Byeongdu; Rajh, Tijana; Morin, Rachel; Pelton, Matthew (ACS Publications, 2020-10-19)
      We show that the self-assembly of monodisperse CdSe nanocrystals synthesized at lower temperature (∼310 °C) into three-dimensional supercrystals results in the formation of separate regions within the supercrystals that ...
    • VLBA Polarimetry: A Faraday Screen in 3C 273 

      Ojha, Roopesh; Homan, Daniel C.; Wardle, John F. C.; Roberts, David H.; Aller, Hugh D.; Aller, Margo F.; Hughes, Philip A. (Astronomical Society of the Pacific Conference Series, 2005)
      The polarization of superluminal radio components moving at the base of the VLBI jet in 3C273 are tracked as part of a six epoch monitoring campaign at 15 and 22 GHz. The components rise sharply in fractional polarization ...
    • VLBA Snap-Shot Imaging of Scintillating Sources 

      Ojha, Roopesh; Lovell, James E.; Jauncey, David L.; Kedziora-Chudczer, Lucyna; Bignall, Hayley E.; Reynolds, John E.; Tzioumis, Anastasios K.; Macquart, Jean-Pierre; Fey, Alan L.; Johnston, Kenneth J. (Astronomical Society of the Pacific Conference Series, 2005)
      We present VLBA snap-shot images of weak scintillating sources and compare their morphologies with those of strong scintillating sources imaged by the USNO astrometry program. It is now clear that interstellar scintillation ...
    • VLBA Snapshot Imaging Survey of Scintillating Sources 

      Ojha, Roopesh; Fey, Alan L.; Lovell, James E. J.; Jauncey, David L.; Johnston, Kenneth J. (IOP, 2004-10-01)
      We present 8.4 GHz Very Long Baseline Array (VLBA) observations of 75 extragalactic radio sources drawn from the scintillating sources discovered in the Microarcsecond Scintillation-induced Variability survey. This survey ...
    • VLBI Monitoring of the bright γ-ray blazar PKS 0537−441 

      Hungwe, F.; Ojha, R.; Kadler, M.; Booth, R.; Blanchard, J.; Lovell, J.; Muller, C.; Bock, M.; TANAMI team (2010-06-10)
      One of the defining characteristics of BL Lacertae objects is their strong variability across the electromagnetic spectrum. PKS 0537-441 is one such object and is one of the most luminous blazars from radio to gamma-ray ...
    • VLBI Observations of Southern Hemisphere ICRF Sources. I. 

      Ojha, Roopesh; Fey, Alan L.; Johnston, Kenneth J.; Jauncey, David L.; Reynolds, John E.; Tzioumis, Anastasios K.; Quick, Jonathan F. H.; Nicolson, George D.; Ellingsen, Simon P.; Dodson, Richard G.; McCulloch, Peter M. (IOP, 2004-06-01)
      We present 8.4 GHz very long baseline interferometry (VLBI) observations of 69 southern hemisphere extragalactic sources in the International Celestial Reference Frame. These are the first in a series of observations ...
    • VLBI Observations of Southern Hemisphere ICRF Sources. II. Astrometric Suitability Based on Intrinsic Structure 

      Ojha, Roopesh; Fey, Alan L.; Charlot, Patrick; Jauncey, David L.; Johnston, Kenneth J.; Reynolds, John E.; Tzioumis, Anastasios K.; Quick, Jonathan F. H.; Nicolson, George D.; Ellingsen, Simon P.; McCulloch, Peter M.; Koyama, Yasuhiro (IOP, 2005-12-01)
      We present 8.4 GHz very long baseline interferometry (VLBI) observations of 48 southern hemisphere extragalactic sources from the International Celestial Reference Frame. These are the second in a series of observations ...
    • VLBI Observations of the Gigahertz-Peaked Spectrum Galaxy PKS 1934−638 

      Ojha, Roopesh; Fey, Alan L.; Johnston, Kenneth J.; Tzioumis, Anastasios K.; Reynolds, John E. (IOP, 2004-04-01)
      We present 8.4 GHz VLBI observations of the gigahertz-peaked spectrum source PKS 1934-638 made with the Australian Long Baseline Array. Our observations confirm the compact double nature of the source and yield measured ...
    • VLBI studies of TANAMI radio galaxies 

      Angioni, Roberto; Rösch, Florian; Ros, Eduardo; Kadler, Matthias; Ojha, Roopesh; Müller, Cornelia; Schulz, Robert; TANAMI collaboration (2016-12-07)
      Radio galaxies are relatively faint at γ-ray energies, where they make up only 1-2% of all AGN detected by Fermi-LAT. However, they offer a unique perspective to study the intrinsic properties of AGN jets. For this reason, ...