815 research outputs found
Revealing the spectral state transition of the Clocked Burster, GS 1826-238 with NuSTAR StrayCats
We present the long term analysis of GS 1826-238, a neutron star X-ray binary
known as the "Clocked Burster", using data from NuSTAR StrayCats. StrayCats, a
catalogue of NuSTAR stray light data, contains data from bright, off-axis X-ray
sources that have not been focused by the NuSTAR optics. We obtained stray
light observations of the source from 2014-2021, reduced and analyzed the data
using nustar-gen-utils Python tools, demonstrating the transition of source
from the "island" atoll state to a "banana" branch. We also present the
lightcurve analysis of Type I X-Ray bursts from the Clocked Burster and show
that the bursts from the banana/soft state are systematically shorter in
durations than those from the island/hard state and have a higher burst
fluence. From our analysis, we note an increase in mass accretion rate of the
source, and a decrease in burst frequency with the transition
Radiation Pressure Dominate Regime of Relativistic Ion Acceleration
The electromagnetic radiation pressure becomes dominant in the interaction of
the ultra-intense electromagnetic wave with a solid material, thus the wave
energy can be transformed efficiently into the energy of ions representing the
material and the high density ultra-short relativistic ion beam is generated.
This regime can be seen even with present-day technology, when an exawatt laser
will be built. As an application, we suggest the laser-driven heavy ion
collider.Comment: 10 pages, 4 figure
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The effect of videokeratoscope faceplate design on radius of curvature maps
A computer model using finite ray tracing methods was developed to simulate a videokeratoscope analysing an average cornea. Different faceplate designs were tested using five points in the faceplate subtending angles between 15 and 75 in 15 intervals at the corneal vertex. Image quality was assessed by adding the geometrical blurs of the 5 image points. Differences (error) between accurate sagittal radius of curvature and sagittal radius of curvature calculated by the van Saarloos algorithm were calculated for selected surfaces at the same corneal points. The calculations were repeated for the tangential radius of curvature. Differences equal or bigger than 0.02 mm were regarded as clinically significant. The surface that provided the sharpest image for an average cornea was a cylinder with the base 120 mm away from the corneal vertex and a diameter of 26 mm. Changing the faceplate design results in clinically significant differences for an average cornea
Two-pion correlations in Au+Au collisions at 10.8 GeV/c per nucleon
Two-particle correlation functions for positive and negative pions have been
measured in Au+Au collisions at 10.8~GeV/c per nucleon. The data were analyzed
using one- and three-dimensional correlation functions. From the results of the
three-dimensional fit the phase space density of pions was calculated. It is
consistent with local thermal equilibrium.Comment: 5 pages RevTeX (including 3 Figures
Measuring the masses of magnetic white dwarfs: A NuSTAR Legacy Survey
The hard X-ray spectrum of magnetic cataclysmic variables can be modelled to
provide a measurement of white dwarf mass. This method is complementary to
radial velocity measurements, which depend on the (typically rather uncertain)
binary inclination. Here we present results from a Legacy Survey of 19 magnetic
cataclysmic variables with NuSTAR. We fit accretion column models to their
20-78 keV spectra and derive the white dwarf masses, finding a weighted average
, with a standard deviation
, when we include the masses derived from previous
NuSTAR observations of seven additional magnetic cataclysmic variables. We find
that the mass distribution of accreting magnetic white dwarfs is consistent
with that of white dwarfs in non-magnetic cataclysmic variables. Both peak at a
higher mass than the distributions of isolated white dwarfs and
post-common-envelope binaries. We speculate as to why this might be the case,
proposing that consequential angular momentum losses may play a role in
accreting magnetic white dwarfs and/or that our knowledge of how the white
dwarf mass changes over accretion-nova cycles may also be incomplete.Comment: 14 pages. 5 figures in main paper, 1 figure in appendix. Accepted for
publication in MNRA
Directed flow of antiprotons in Au+Au collisions at AGS
Directed flow of antiprotons is studied in Au+Au collisions at a beam
momentum of 11.5A GeV/c. It is shown that antiproton directed flow is
anti-correlated to proton flow. The measured transverse momentum dependence of
the antiproton flow is compared with predictions of the RQMD event generator.Comment: 16 pages, 6 figure
Proton and Pion Production in Au+Au Collisions at 10.8A GeV/c
We present proton and pion tranverse momentum spectra and rapidity
distributions for Au+Au collisions at 10.8A GeV/c. The proton spectra exhibit
collective transverse flow effects. Evidence of the influence of the Coulomb
interaction from the fireball is found in the pion transverse momentum spectra.
The data are compared with the predictions of the RQMD event generator.Comment: plain tex (revtex), 24 pages Submitted to Phys. Rev.
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