40,959 research outputs found
Ultraviolet/X-ray variability and the extended X-ray emission of the radio-loud broad absorption line quasar PG 1004+130
We present the results of recent Chandra, XMM-Newton, and Hubble Space
Telescope observations of the radio-loud (RL), broad absorption line (BAL)
quasar PG 1004+130. We compare our new observations to archival X-ray and UV
data, creating the most comprehensive, high signal-to-noise, multi-epoch,
spectral monitoring campaign of a RL BAL quasar to date. We probe for
variability of the X-ray absorption, the UV BAL, and the X-ray jet, on
month-year timescales. The X-ray absorber has a low column density of
cm when it is assumed to be fully
covering the X-ray emitting region, and its properties do not vary
significantly between the 4 observations. This suggests the observed absorption
is not related to the typical "shielding gas" commonly invoked in BAL quasar
models, but is likely due to material further from the central black hole. In
contrast, the CIV BAL shows strong variability. The equivalent width (EW) in
2014 is EW=11.240.56 \AA, showing a fractional increase of =1.160.11 from the 2003 observation, 3183 days earlier
in the rest-frame. This places PG 1004+130 among the most highly variable BAL
quasars. By combining Chandra observations we create an exposure 2.5 times
deeper than studied previously, with which to investigate the nature of the
X-ray jet and extended diffuse X-ray emission. An X-ray knot, likely with a
synchrotron origin, is detected in the radio jet ~8 arcsec (30 kpc) from the
central X-ray source with a spatial extent of ~4 arcsec (15 kpc). No similar
X-ray counterpart to the counterjet is detected. Asymmetric, non-thermal
diffuse X-ray emission, likely due to inverse Compton scattering of Cosmic
Microwave Background photons, is also detected.Comment: 15 pages, 7 figures, 3 tables. Accepted for publication in Ap
Dynamic Monte Carlo Study of the Two-Dimensional Quantum XY Model
We present a dynamic Monte Carlo study of the Kosterlitz-Thouless phase
transition for the spin-1/2 quantum XY model in two dimensions. The short-time
dynamic scaling behaviour is found and the dynamical exponent , and
the static exponent are determined at the transition temperature.Comment: 6 pages with 3 figure
X-ray Insights into the Nature of Quasars with Redshifted Broad Absorption Lines
We present observations of seven broad absorption line (BAL)
quasars at -2.516 with redshifted BAL troughs (RSBALs). Five of our
seven targets were detected by in 4-13 ks exposures with ACIS-S. The
values, values, and spectral energy
distributions of our targets demonstrate they are all X-ray weak relative to
expectations for non-BAL quasars, and the degree of X-ray weakness is
consistent with that of appropriately-matched BAL quasars generally.
Furthermore, our five detected targets show evidence for hard X-ray spectral
shapes with a stacked effective power-law photon index of . These findings support the presence of heavy X-ray
absorption ( cm) in RSBAL quasars,
likely by the shielding gas found to be common in BAL quasars more generally.
We use these X-ray measurements to assess models for the nature of RSBAL
quasars, finding that a rotationally-dominated outflow model is favored while
an infall model also remains plausible with some stipulations. The X-ray data
disfavor a binary quasar model for RSBAL quasars in general.Comment: 11 pages, 5 figures, and 3 table
Dynamic Approach to the Fully Frustrated XY Model
Using Monte Carlo simulations, we systematically investigate the
non-equilibrium dynamics of the chiral degree of freedom in the two-dimensional
fully frustrated XY model. The critical initial increase of the staggered
chiral magnetization is observed. By means of the short-time dynamics approach,
we estimate the second order phase transition temperature and all the
dynamic and static critical exponents , z, and .Comment: 5 pages with 6 figures include
- …