5,402 research outputs found
The X-ray Nature of Nucleus in Seyfert 2 Galaxy NGC 7590
We present the result of the Chandra high-resolution observation of the
Seyfert~2 galaxy NGC 7590. This object was reported to show no X-ray absorption
in the low-spatial resolution ASCA data. The XMM observations show that the
X-ray emission of NGC 7590 is dominated by an off-nuclear ultra-luminous X-ray
source (ULX) and an extended emission from the host galaxy, and the nucleus is
rather weak, likely hosting a Compton-thick AGN. Our recent Chandra observation
of NGC 7590 enables to remove the X-ray contamination from the ULX and the
extended component effectively. The nuclear source remains undetected at
~4x10^{-15} erg/s/cm^-2 flux level. Although not detected, Chandra data gives a
2--10 keV flux upper limit of ~6.1x10^{-15} erg/s/cm^-2 (at 3 sigma level), a
factor of 3 less than the XMM value, strongly supporting the Compton-thick
nature of the nucleus. In addition, we detected five off-nuclear X-ray point
sources within the galaxy D25 ellipse, all with 2 -- 10 keV luminosity above
2x10^{38} erg/s (assuming the distance of NGC 7590). Particularly, the ULX
previously identified by ROSAT data was resolved by Chandra into two distinct
X-ray sources. Our analysis highlights the importance of high spatial
resolution images in discovering and studying ULXs.Comment: 8 pages, 5 figures, RAA accepte
Development of rheometer for semi-solid highmelting point alloys
A rheometer for semi-solid high-melting point alloys was developed based on the principle of a double-bucket rheometer, with which the solidifying of semi-solid high-melting point alloy melt could be effectively controlled by the control of temperature and the outer force-field; and different microstructures have also been obtained. This rheometer can be used to investigate the rheological behavior under different conditions by changing the Theological parameters. By way of full-duplex communication between the computer and each sensor, automatic control of the test equipment and real- timemeasurement of rheological parameters were realized. Finally, the influencing factors on torque are also quantitatively analyzed
The classical nature of nuclear spin noise near clock transitions of Bi donors in silicon
Whether a quantum bath can be approximated as classical noise is a
fundamental issue in central spin decoherence and also of practical importance
in designing noise-resilient quantum control. Spin qubits based on bismuth
donors in silicon have tunable interactions with nuclear spin baths and are
first-order insensitive to magnetic noise at so-called clock-transitions (CTs).
This system is therefore ideal for studying the quantum/classical nature of
nuclear spin baths since the qubit-bath interaction strength determines the
back-action on the baths and hence the adequacy of a classical noise model. We
develop a Gaussian noise model with noise correlations determined by quantum
calculations and compare the classical noise approximation to the full quantum
bath theory. We experimentally test our model through dynamical decoupling
sequence of up to 128 pulses, finding good agreement with simulations and
measuring electron spin coherence times approaching one second - notably using
natural silicon. Our theoretical and experimental study demonstrates that the
noise from a nuclear spin bath is analogous to classical Gaussian noise if the
back-action of the qubit on the bath is small compared to the internal bath
dynamics, as is the case close to CTs. However, far from the CTs, the
back-action of the central spin on the bath is such that the quantum model is
required to accurately model spin decoherence.Comment: 5 pages, 3 figure
Quantum properties of fermionic fields in multi-event horizon spacetime
We investigate the properties of quantum entanglement and mutual information
in the multi-event horizon Schwarzschild-de Sitter (SdS) spacetime for massless
Dirac fields. We obtain the expression for the evolutions of the quantum state
near the black hole event horizon (BEH) and cosmological event horizon (CEH) in
the SdS spacetime. Under the Nariai limit, the physically accessible
entanglement and mutual information are maximized, and the physically
inaccessible correlations are zero. With the increase in temperature of either
horizon, the physically accessible correlations experience degradation.
Notably, the initial state remains entangled and can be utilized in
entanglement-based quantum information processing tasks, which differs form the
scalar field case. Furthermore, the degradation of physically accessible
correlations is more pronounced for small-mass black holes. In contrast, the
physically inaccessible correlations separated by the CEH monotonically
increase with the radiation temperature, and such correlations are not
decisively influenced by the effect of particle creation at the BEH. Moreover,
a similar phenomenon is observed for the inaccessible correlations separated by
the BEH. This result differs from the single event spacetime, in which the
physically inaccessible entanglement is a monotonic function of the Hawking
temperature.Comment: 14 pages, 7 figure
- …