4,561 research outputs found
X-ray outbursts of low-mass X-ray binary transients observed in the RXTE era
We have performed a statistical study of the properties of 110 bright X-ray
outbursts in 36 low-mass X-ray binary transients (LMXBTs) seen with the All-Sky
Monitor (2--12 keV) on board the {\it Rossi X-ray Timing Explorer} ({\it RXTE})
in 1996--2011. We have measured a number of outburst properties, including peak
X-ray luminosity, rate of change of luminosity on a daily timescale,
-folding rise and decay timescales, outburst duration, and total radiated
energy. We found that the average properties such as peak X-ray luminosity,
rise and decay timescales, outburst duration, and total radiated energy of
black hole LMXBTs, are at least two times larger than those of neutron star
LMXBTs, implying that the measurements of these properties may provide
preliminary clues as to the nature of the compact object of a newly discovered
LMXBT. We also found that the outburst peak X-ray luminosity is correlated with
the rate of change of X-ray luminosity in both the rise and the decay phases,
which is consistent with our previous studies. Positive correlations between
total radiated energy and peak X-ray luminosity, and between total radiated
energy and the -folding rise or decay timescale, are also found in the
outbursts. These correlations suggest that the mass stored in the disk before
an outburst is the primary initial condition that sets up the outburst
properties seen later. We also found that the outbursts of two transient
stellar-mass ULXs in M31 also roughly follow the correlations, which indicate
that the same outburst mechanism works for the brighter outbursts of these two
sources in M31 that reached the Eddington luminosity.Comment: Accepted to Ap
Low Frequency Quasi-periodic Oscillation in MAXI J1820+070: Revealing distinct Compton and Reflection Contributions
X-ray low frequency quasi-periodic oscillations (LFQPOs) of black hole X-ray
binaries, especially those type-C LFQPOs, are representative timing signals of
black hole low/hard state and intermediate state, which has been suspected as
to originate due to Lense-Thirring precession of the accretion flow. Here we
report an analysis of one of the \emph{Insight}-HXMT observations of the black
hole transient MAXI J1820070 taken near the flux peak of its hard spectral
state during which strong type-C LFQPOs were detected in all three instruments
up to photon energies above 150 keV. We obtained and analyzed the
short-timescale X-ray spectra corresponding to high- and low-intensity phases
of the observed LFQPO waveform with a spectral model composed of Comptonization
and disk reflection components. We found that the normalization of the spectral
model is the primary parameter that varied between the low and high-intensity
phases. The variation in the LFQPO flux at the hard X-ray band (> 100 keV) is
from the Compton component alone, while the energy-dependent variation in the
LFQPO flux at lower energies (< 30 keV) is mainly caused by the reflection
component with a large reflection fraction in response to the incident Compton
component. The observed X-ray LFQPOs thus should be understood as manifesting
the original timing signals or beats in the hard Compton component, which gives
rise to additional variability in softer energies due to disk reflection.Comment: 8 pages, 4 figures, accepted for publication in MNRA
An apparent positive relation between spin and orbital angular momentum in X-ray binaries
The origin of current angular momentum (AM) of the black hole (BH) in X-ray
binary (XRB) is still unclear, which is related with the birth and/or the
growth of the BH. Here we collect the spin parameters measured in BH
XRBs and find an apparent bimodal distribution centered at 0.17 and
0.83. We find a positive relation between the spin parameter and the orbital
period/orbital separation through combining distinct XRB categories, including
neutron star (NS) low-mass X-ray binaries (LMXBs), Roche-lobe overflow (RLOF)
BH XRBs and wind-fed BH XRBs. It seems that the AM of the compact star and the
binary orbit correlates by combining the different XRB systems. These positive
relations imply that accretion process is a common mechanism for spinning up
the compact star in these diverse XRB systems. We infer that the low and high
spin BH XRBs may experience different evolution and accretion history, which
corresponds to the bimodal distribution of the BH spin parameters. The low spin
BHs () are similar to the NS LMXBs, the compact star of which is
spun-up by the low-level accretion, and the high spin BHs () had
experienced a short hypercritical accretion ()
period, during which, the BH spin dramatically increased.Comment: 13 pages, 7 figures, accepted for publication in MNRA
A Robust Quantum Random Access Memory
A "bucket brigade" architecture for a quantum random memory of memory
cells needs times of quantum manipulation on control circuit nodes
per memory call. Here we propose a scheme, in which only average times
manipulation is required to accomplish a memory call. This scheme may
significantly decrease the time spent on a memory call and the average overall
error rate per memory call. A physical implementation scheme for storing an
arbitrary state in a selected memory cell followed by reading it out is
discussed.Comment: 5 pages, 3 figure
Clinical efficacy of radiotherapy combined with sodium glycididazole in the treatment of recurrent oesophageal carcinoma
Purpose: To assess the clinical efficacy and side effects of radiotherapy combined with sodium glycididazole in the treatment of recurrent esophageal carcinoma.Methods: Ninety patients with locally recurrent oesophageal carcinoma who were admitted to the Oncology Department at Taian City Central Hospital, Shandong, China, were randomly divided into a treatment group (treated with radiotherapy and sodium glycididazole) and a control group (treated with radiotherapy alone) in a randomized study. Short-term curative effects, median progression-free survival (PFS), and side effects were compared between the two groups.Results: The cure rate in the treatment group was 86.70 %, whereas that in the control group was 51.10 % (p < 0.05). Median PFS in the treatment group was 9.9 months versus 5.3 months in the control group (p < 0.05). Side effects in both groups included alopecia, headache, nausea, vomiting and leucopaenia, at level one or two. In this regard, the difference between the two groups was statistically insignificant (p > 0.05).Conclusion: Radiotherapy combined with sodium glycididazole shows a higher short-term curative effect in the treatment of recurrent oesophageal carcinoma than radiotherapy alone.Keywords: Alopecia, Leucopaenia, Oesophageal carcinoma, Radiotherapy, Sodium glycididazol
- …