166 research outputs found
XMM-Newton Observations of NGC 247: X-ray Population and a Supersoft Ultraluminous X-ray Source
We report on a new XMM-Newton observation of NGC 247 from December 2009. The
galaxy contains a supersoft, ultraluminous X-ray source (ULX) whose spectrum
consists of a thermal component with a temperature about 0.1 keV and a
power-law tail with a photon index around 2.5. The thermal emission is
absolutely the dominant component, contributing 96% of the total luminosity in
the 0.3-10 keV band. Variability is detected at timescales of 10^2 s and longer
with a \nu^-1 power spectrum. These properties are consistent with black hole
binaries in the thermal state and suggest the presence of an intermediate mass
black hole of at least 600 solar masses. However, the integrated rms power is
much higher than typically found in the thermal state. An alternative
explanation of the emission could be a photosphere with a radius about 10^9 cm.
A possible absorption feature around 1 keV is detected, which may be due to
absorption of highly ionized winds. X-ray sources within the disk of NGC 247
have a luminosity function consistent with that found in low mass X-ray
binaries. We confirm previous results that X-rays from the quasar PHL 6625 may
be absorbed by gas in NGC 247, mainly at energies below 0.3 keV.Comment: accepted for publication in the Astrophysical Journa
Determination of QPO properties in the presence of strong broad-band noise: a case study on the data of MAXI J1820+070
Accurate calculation of the phase lags of quasi-periodic oscillations (QPOs)
will provide insight into their origin. In this paper we investigate the phase
lag correction method which has been applied to calculate the intrinsic phase
lags of the QPOs in MAXI J1820+070. We find that the traditional additive model
between BBN and QPOs in the time domain is rejected, but the convolution model
is accepted. By introducing a convolution mechanism in the time domain, the
Fourier cross-spectrum analysis shows that the phase lags between QPOs
components in different energy bands will have a simple linear relationship
with the phase lags between the total signals, so that the intrinsic phase lags
of the QPOs can be obtained by linear correction. The power density spectrum
(PDS) thus requires a multiplicative model to interpret the data. We briefly
discuss a physical scenario for interpreting the convolution. In this scenario,
the corona acts as a low-pass filter, the Green's function containing the noise
is convolved with the QPOs to form the low-frequency part of the PDS, while the
high-frequency part requires an additive component. We use a multiplicative PDS
model to fit the data observed by Insight-HXMT. The overall fitting results are
similar compared to the traditional additive PDS model. Neither the width nor
the centroid frequency of the QPOs obtained from each of the two PDS models
were significantly different, except for the r.m.s. of the QPOs. Our work thus
provides a new perspective on the coupling of noise and QPOs.Comment: 13 pages, 8 figure
Synthesis, phase diagram and magnetic properties of (1-x)BiFeO3-xLaMnO(3) Solid Solution
通讯作者地址: Wu, JTIn this paper, we report the syntheses of (1 - x) BiFeO3-xLaMnO(3) solid solution (x = 0-1) by an improved sol-gel method. With careful characterization of crystal structures of the as-prepared products and the phase transition as a function of temperature, the phase diagram of (1 - x) BiFeO3-xLaMnO(3) solid solution has been determined. With the increasing of x value, the crystal structure of the samples transforms from rhombohedral R3c (x 0.08).National Basic Research Program of China
2011CBA00508
2015CB932301
National Natural Science Foundation of China
21333008
21131005
2140113
Storage of multiple single-photon pulses emitted from a quantum dot in a solid-state quantum memory
Quantum repeaters are critical components for distributing entanglement over
long distances in presence of unavoidable optical losses during transmission.
Stimulated by Duan-Lukin-Cirac-Zoller protocol, many improved quantum-repeater
protocols based on quantum memories have been proposed, which commonly focus on
the entanglement-distribution rate. Among these protocols, the elimination of
multi-photons (multi-photon-pairs) and the use of multimode quantum memory are
demonstrated to have the ability to greatly improve the
entanglement-distribution rate. Here, we demonstrate the storage of
deterministic single photons emitted from a quantum dot in a
polarization-maintaining solid-state quantum memory; in addition,
multi-temporal-mode memory with , and narrow single-photon pulses
is also demonstrated. Multi-photons are eliminated, and only one photon at most
is contained in each pulse. Moreover, the solid-state properties of both
sub-systems make this configuration more stable and easier to be scalable. Our
work will be helpful in the construction of efficient quantum repeaters based
on all-solid-state devicesComment: Published version, including supplementary materia
Evidence for an intermediate line region in AGN's inner torus region and its evolution from narrow to broad line Seyfert I galaxies
A two-components model for Broad Line Region (BLR) of Active Galactic Nuclei
(AGN) has been suggested for many years but not widely accepted (e.g., Hu et
al. 2008; Sulentic et al. 2000; Brotherton et al. 1996; Mason et al. 1996).
This model indicates that the broad line can be described with superposition of
two Gaussian components (Very Broad Gaussian Component (VBGC) and InterMediate
Gaussian Component (IMGC)) which are from two physically distinct regions;
i.e., Very Broad Line Region (VBLR) and InterMediate Line Region (IMLR). We
select a SDSS sample to further confirm this model and give detailed analysis
to the geometry, density and evolution of these two regions. Micro-lensing
result of BLR in J1131-1231 and some unexplained phenomena in Reverberation
Mapping (RM) experiment provide supportive evidence for this model. Our results
indicate that the radius obtained from the emission line RM normally
corresponds to the radius of the VBLR, and the existence of the IMGC may affect
the measurement of the black hole masses in AGNs. The deviation of NLS1s from
the M-sigma relation and the Type II AGN fraction as a function of luminosity
can be explained in this model in a coherent way. The evolution of the two
emission regions may be related to the evolutionary stages of the broad line
regions of AGNs from NLS1s to BLS1s. Based on the results presented here, a
unified picture of hierarchical evolution of black hole, dust torus and galaxy
is proposed.Comment: 58 pages, 19 figures, 1 table. Matches the published versio
Serum cytokine change profile associated with HBsAg loss during combination therapy with PEG-IFN-α in NAs-suppressed chronic hepatitis B patients
ObjectiveThe aim of this study was to explore the profile of cytokine changes during the combination therapy with pegylated interferon alpha (PEG-IFN-α) and its relationship with HBsAg loss in nucleos(t)ide analogs (NAs)-suppressed chronic hepatitis B patients.MethodsSeventy-six patients with chronic hepatitis B with HBsAg less than 1,500 IU/ml and HBV DNA negative after receiving ≥ 1-year NAs therapy were enrolled. Eighteen patients continued to take NAs monotherapy (the NAs group), and 58 patients received combination therapy with NAs and PEG-IFN-α (the Add-on group). The levels of IFNG, IL1B, IL1RN, IL2, IL4, IL6, IL10, IL12A, IL17A, CCL2, CCL3, CCL5, CXCL8, CXCL10, TNF, and CSF2 in peripheral blood during treatment were detected.ResultsAt week 48, 0.00% (0/18) in the NAs group and 25.86% (15/58) in the Add-on group achieved HBsAg loss. During 48 weeks of combined treatment, there was a transitory increase in the levels of ALT, IL1RN, IL2, and CCL2. Compared to the NAs group, CXCL8 and CXCL10 in the Add-on group remain higher after rising, yet CCL3 showed a continuously increasing trend. Mild and early increases in IL1B, CCL3, IL17A, IL2, IL4, IL6, and CXCL8 were associated with HBsAg loss or decrease >1 log, while sustained high levels of CCL5 and CXCL10 were associated with poor responses to Add-on therapy at week 48.ConclusionsThe serum cytokine change profile is closely related to the response to the combination therapy with PEG-IFN-α and NAs, and may help to reveal the mechanism of functional cure and discover new immunological predictors and new therapeutic targets
Hilbert-Huang Transform analysis of quasi-periodic oscillations in MAXI J1820+070
We present time-frequency analysis, based on the Hilbert-Huang transform
(HHT), of the evolution on the low-frequency quasi-periodic oscillations
(LFQPOs) observed in the black hole X-ray binary MAXI J1820+070. Through the
empirical mode decomposition (EMD) method, we decompose the light curve of the
QPO component and measure its intrinsic phase lag between photons from
different energy bands. We find that the QPO phase lag is negative (low energy
photons lag behind high energy photons), meanwhile the absolute value of the
lag increases with energy. By applying the Hilbert transform to the light curve
of the QPO, we further extract the instantaneous frequency and amplitude of the
QPO. Compared these results with those from the Fourier analysis, we find that
the broadening of the QPO peak is mainly caused by the frequency modulation.
Through further analysis, we find that these modulations could share a common
physical origin with the broad-band noise, and can be well explained by the
internal shock model of the jet
- …