252,445 research outputs found
Exploring the Nature of Weak Chandra Sources near the Galactic Centre
We present results from the first near-IR imaging of the weak X-ray sources
discovered in the Chandra/ACIS-I survey (Wang et al. 2002) towards the Galactic
Centre (GC). These ~800 discrete sources, which contribute significantly to the
GC X-ray emission, represent an important and previously unknown population
within the Galaxy. From our VLT observations we will identify likely IR
counterparts to a sample of the hardest sources, which are most likely X-ray
binaries. With these data we can place constraints on the nature of the
discrete weak X-ray source population of the GC.Comment: In Proc. of ``Interacting Binaries: Accretion, Evolution, and
Outcomes'', eds. L. A. Antonelli et al., AIP, Cefalu, Sicily, 200
Uniqueness of asymptotic cones of complete noncompact shrinking gradient Ricci solitons with Ricci curvature decay
We discuss an elementary consequence of the works of (1) Brett Kotschwar and
Lu Wang and (2) Ovidiu Munteanu and Jiaping Wang
Probing the X-ray Variability of X-ray Binaries
Kilohertz quasi-periodic oscillations (kHz QPOs) has been regarded as
representing the Keplerian frequency at the inner disk edge in the neutron star
X-ray binaries. The so-called ``parallel tracks'' on the plot of the kHz QPO
frequency vs. X-ray flux in neutron star X-ray binaries, on the other hand,
show the correlation between the kHz QPO frequency and the X-ray flux on time
scales from hours to days. This is suspected as caused by the variations of the
mass accretion rate through the accretion disk surrounding the neutron star. We
show here that by comparing the correlation between the kHz QPO frequency and
the X-ray count rate on a certain QPO time scale observed approximately
simultaneous in the Fourier power spectra of the X-ray light curve, we have
found evidences that the X-ray flux of millihertz QPOs in neutron star X-ray
binaries is generated inside the inner disk edge if adopting that the kilohertz
QPO frequency is an orbital frequency at the inner disk edge. This approach
could be applied to other variability components in X-ray binaries.Comment: 4 pages including 1 figure, To appear in "High Energy Processes and
Phenomena in Astrophysics, IAU Symposium 214", X. Li, Z. Wang, V. Trimble
(eds
Jing Wang. High culture fever : politics, aesthetics, and ideology in Deng\u27s China; Jing Wang, ed. China\u27s avant-garde fiction : an anthology
This article reviews the books High Culture Fever: Politics, Aesthetics, and Ideology in Deng\u27s China written by Jing Wang and China\u27s Avant-Garde Fiction: An Anthology edited by Jing Wang
Radiation Mechanism of the Soft Gamma-ray Pulsar PSR B1509-58
The outer gap model is used here to explain the spectrum and the energy
dependent light curves of the X-ray and soft gamma-ray radiations of the
spin-down powered pulsar PSR B1509-58.In the outer gap model, most pairs inside
the gap are created around the null charge surface and the gap's electric field
separates the two charges to move in opposite directions. Consequently, the
region from the null charge surface to the light cylinder is dominated by the
outflow of particles and that from the null charge surface to the star is
dominated by the inflow of particles. The inflow and outflow of particles move
along the magnetic field lines and emit curvature photons, and the incoming
curvature photons are converted to pairs by the strong magnetic field of the
star. These pairs emit synchrotron photons. We suggest that the X-rays and soft
gamma-rays of PSR B1509-58 result from the synchrotron radiation of these
pairs, and the viewing angle of PSR B1509-58 only receives the inflow
radiation. The magnetic pair creation requires a large pitch angle, which makes
the pulse profile of the synchrotron radiation distinct from that of the
curvature radiation. We carefully trace the pulse profiles of the synchrotron
radiation with different pitch angles. We find that the differences between the
light curves of different energy bands are due to the different pitch angles of
the secondary pairs, and the second peak appearing at E>10MeV comes from the
region near the star, where the stronger magnetic field allows the pair
creation to happen with a smaller pitch angle.Comment: 5 pages, 8 figures, 2012 Fermi Symposium proceedings - eConf C12102
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