117018554
Bursty Variations of Jovian 6cm Radio Emissions and Quasi-Periodic Jupiter's Polar Activities
In reference to Jupiter south polar quasi-periodic 40-50 min (QP-40) activities and the model scenario for global QP-40 oscillations of the Jovian inner radiation belt (IRB), we validate relevant predictions and confirmations by amassing empirical evidence from Ulysses, Cassini, Chandra, Galileo, XMM-Newton, and Advanced Composition Explorer for Jupiter north polar QP-40 activities. We report ground 6cm radio observations of Jupiter by Urumqi 25m telescope for synchrotron intensity bursty variations of the Jovian IRB and show their likely correlations with the recurrent arrival of high-speed solar winds at Jupiter.
118516843
Intra-day variability observations of S5 0716+714 over 4.5 years at 4.8 GHz
Aims. We aim to search for evidence of annual modulation in the time scales of the BL Lac object S5 0716+714.
119209019
On the influence of the Sun on the rapid variability of compact extragalactic sources
Since December 2004, we have performed a program to monitor intraday variable sources at a frequency of 5 GHz at the Urumqi Observatory. We present our analysis of the variability characteristics of the flat-spectrum radio source AO 0235 + 164, which detects an annual cycle in the variability amplitude. This appears to correlate with the solar elongation of the source. A thorough analysis of the results of the MASIV IDV survey - which provides the variability characteristics of a large sample of compact radio sources confirms that there is a small but detectable component of the observed fractional modulation that increases with decreasing solar elongation. We discuss the hypothesis that the phenomenon is related to interplanetary scintillation.
16003577
J1128+592: a highly variable IDV source
Short time-scale radio variations of compact extragalactic radio quasars and blazars known as IntraDay Variability (IDV) can be explained in at least some sources as a propagation effect; the variations are interpreted as scintillation of radio waves in the turbulent interstellar medium of the Milky Way. One of the most convincing observational arguments in favor of a propagation-induced variability scenario is the observed annual modulation in the characteristic time scale of the variation due to the Earth's orbital motion. So far there are only two sources known with a well-constrained seasonal cycle. Annual modulation has been proposed for a few other less well-documented objects. However, for some other IDV sources source-intrinsic structural variations which cause drastic changes in the variability time scale were also suggested. J1128+592 is a recently discovered, highly variable IDV source. Previous, densely time-sampled flux-density measurements with the Effelsberg 100-m radio telescope (Germany) and the Urumqi 25-m radio telescope (China), strongly indicate an annual modulation of the time scale. The most recent 4 observations in 2006/7, however, do not fit well to the annual modulation model proposed before. In this paper, we investigate a possible explanation of this discrepancy. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
16178268
The radio lightcurve of SN 2008iz in M82 revealed by Urumqi observations
We report on a set of 5 GHz Urumqi observations of the galaxy M82, made between August 2005 and May 2009. From the resulting flux densities, we detect a strong flare, starting in March or April and peaking in June 2008. We identify this flare with supernova SN 2008iz. The time sampling of the radio light curve allows us to obtain information on the precursor mass-loss rate, the strength of the magnetic field in the radiating region, the explosion date, and the deceleration of the expanding shock. We also check the possible contribution of synchrotron self absorption to the radio light curve and compare our model with other observations of the supernova at 22 GHz.
119257437
Very Long Baseline Array observations of the intraday variable source J1128+592
Context. Short timescale flux density variations in flat spectrum radio sources are often explained by the scattering of radio waves in the turbulent ionized interstellar medium of the Milky Way. One of the most convincing observational arguments in favor of this is the annual modulation of the variability timescale caused by the orbital motion of Earth around the Sun. J1128+5925 is a recently discovered IDV source with a possible annual modulation in its variability timescale. New observations suggest a change in its variability characteristics.
119692613
Measurement of the $B_c^{\pm}$ meson lifetime using $B_c^{\pm} \to J/\psi~\pi^{\pm}$ decays
This thesis describes a measurement of the lifetime of the B± c meson in an exclusive decay channel B± c → J/ ψ π±, where the J/ψ decays as J/ψ → μ+μ- . The measurement uses a data sample with an integrated luminosity of 6.7 fb-1 collected at CDF. This is the first measurement of the B± c meson lifetime in a hadronic channel and the measured lifetime, τ = 0.449 +0.054 -0.048(stat:) ± 0.019(syst:) ps, is in good agreement with previous results obtained from semileptonic decay channel and confirms previous measurements and theoretical predictions.
15616146
Soliton with a pion field in the global color symmetry model
We calculate the property of the global color symmetry soliton with the pion field being included explicitly. The calculated results indicate that the pion field provides a strong attraction so that the eigenenergy of a quark and the mass of a soliton reduce drastically, in contrast to those with only the sigma field.
28563606
200 A GeV Au + Au collisions serve a nearly perfect quark-gluon liquid.
A new robust method to extract the specific shear viscosity (η/s)(QGP) of a quark-gluon plasma (QGP) at temperatures T(c) < T ≲ 2T(c) from the centrality dependence of the eccentricity-scaled elliptic flow v2/ε measured in ultrarelativistic heavy-ion collisions is presented. Coupling viscous fluid dynamics for the QGP with a microscopic transport model for hadronic freeze-out we find for 200 A GeV Au + Au collisions that v2/ε is a universal function of multiplicity density (1/S)(dN(ch)/dy) that depends only on the viscosity but not on the model used for computing the initial fireball eccentricity ε. Comparing with measurements we find 1<4π(η/s)(QGP) < 2.5 where the uncertainty range is dominated by model uncertainties for the values of ε used to normalize the measured v2.
118880227
A Broken Solar Type?II Radio Burst Induced by a Coronal Shock Propagating across the Streamer Boundary
We discuss an intriguing type II radio burst that occurred on 2011 March 27. The dynamic spectrum was featured by a sudden break at about 43 MHz on the well-observed harmonic branch. Before the break, the spectrum drifted gradually with a mean rate of about -0.05 MHz s(-1). Following the break, the spectrum jumped to lower frequencies. The post-break emission lasted for about 3 minutes. It consisted of an overall slow drift which appeared to have a few fast-drift sub-bands. Simultaneous observations from the Solar TErrestrial RElations Observatory and the Solar Dynamics Observatory were also available and are examined for this event. We suggest that the slow-drift period before the break was generated inside a streamer by a coronal eruption driven shock, and the spectral break as well as the relatively wide spectrum after the break is a consequence of the shock crossing the streamer boundary where density drops abruptly. It is suggested that this type of radio bursts can be taken as a unique diagnostic tool for inferring the coronal density structure, as well as the radio-emitting source region.
17687299
Extracting the QGP viscosity from RHIC data—a status report from viscous hydrodynamics
We report recent progress on causal viscous hydrodynamics for relativistic heavy-ion collisions. For fixed specific shear viscosity η/s, uncertainties in the elliptic flow arising from initial conditions, equation of state, bulk viscosity and numerical viscosity, and the treatment of the highly viscous hadronic stage and freeze-out procedure are analysed. A comparison of current viscous hydrodynamic results with experimental data yields a robust upper limit .