A5049825373- Astrophysical Phenomena and Observations
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Software Reliability and Analysis Research
- Safety Systems Engineering in Autonomy
- Photorefractive and Nonlinear Optics
- Adaptive optics and wavefront sensing
- Statistical and numerical algorithms
- Astronomy and Astrophysical Research
- Advanced Fiber Laser Technologies
- Risk and Safety Analysis
- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Software System Performance and Reliability
- Radiation Effects in Electronics
- Software Engineering Research
- Solid State Laser Technologies
Huawei Technologies (China)
2022-2024
Nanjing University
2000-2023
Pennsylvania State University
2021-2022
Collaborative Innovation Center of Advanced Microstructures
2020
National Laboratory of Solid State Microstructures
2000
Abstract We present a systematic X-ray and multiwavelength study of sample 47 active galactic nuclei (AGNs) with reverberation mapping measurements. This includes 21 super-Eddington accreting AGNs 26 sub-Eddington AGNs. Using high-state observations simultaneous UV/optical measurements, we investigate whether exhibit different accretion disk–corona connections compared to find tight correlations between the X-ray-to-UV/optical spectral slope parameter ( α OX ) monochromatic luminosity at...
Abstract We investigate systematically the X-ray emission from type 1 quasars using a sample of 1825 Sloan Digital Sky Survey non-broad absorption line (non-BAL) with Chandra archival observations. A significant correlation is found between X-ray-to-optical power-law slope parameter ( α OX ) and 2500 Å monochromatic luminosity L 2500Å ), weakness quasar assessed via deviation its value that expected this relation. demonstrate existence population non-BAL X-ray-weak quasars, fractions are...
We report the results of a multi-year spectroscopic and photometric monitoring campaign two luminous quasars, PG~0923+201 PG~1001+291, both located at high-luminosity end broad-line region (BLR) size-luminosity relation with optical luminosities above $10^{45}~{\rm erg~s^{-1}}$. is for first time monitored, PG~1001+291 was previously monitored but our has much longer temporal baseline. detect lags variations broad H$\beta$, H$\gamma$, Fe {\sc ii} lines respect to those 5100~{\AA} continuum....
We analyze 1598 serendipitous Chandra X-ray observations of 462 radio-quiet quasars to constrain the frequency extreme amplitude variability that is intrinsic quasar corona and innermost accretion flow. The in this investigation are all spectroscopically confirmed, optically bright ($m_i \leq$ 20.2), contain no identifiable broad absorption lines their optical/ultraviolet spectra. This sample includes spanning $z \approx$ 0.1 - 4 probes on timescales up $\approx$ 12 rest-frame years....
Abstract We utilize recent NuSTAR observations (co-added depth ≈55–120 ks) of PG 1001+054, 1254+047, and PHL 1811 to constrain their hard X-ray (≳5 keV) weakness spectral shapes thus investigate the nature extreme weakness. These quasars showed very weak soft emission, they were proposed be intrinsically weak, with coronae producing continuum emission relative optical/UV emission. However, new suggest an alternative explanation. The 3–24 keV for 1001+054 are likely flat (effective power-law...
Abstract We report strong and rapid X-ray variability found from the super-Eddington accreting quasar SDSS J081456.10+532533.5 at z = 0.1197. It has a black hole mass of 2.7 × 10 7 M ⊙ dimensionless accretion rate ≈4 measured reverberation-mapping observations. showed weak emission in 2021 February Chandra observation, with 2 keV flux density being <?CDATA ${9.6}_{-4.6}^{+11.6}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow>...
Abstract We report the discovery of extreme X-ray variability in a type 1 quasar: SDSS J075101.42+291419.1. It has black hole (BH) mass 1.6 × 10 7 M ⊙ measured from reverberation mapping, and BH is accreting with super-Eddington accretion rate. Its XMM-Newton observation 2015 May reveals flux drop by factor ∼22 respect to Swift 2013 when it showed typical level emission relative its UV/optical emission. The lack correlated UV results steep X-ray-to-optical power-law slope ( α OX ) −1.97 low...
Abstract We report a dramatic, fast X-ray dimming event in z = 2.627 radio-quiet type 1 quasar, which has an estimated supermassive black hole (SMBH) mass of 6.3 × 10 9 M ⊙ . In the high state, it showed typical level emission relative to its UV/optical emission. Then 0.5–2 keV (rest-frame 1.8–7.3 keV) flux dropped by factor ≈7.6 within two rest-frame days. The is associated with spectral hardening, as 2–7 7.3–25.4 only 17%, and effective power-law photon index spectrum changed from ≈2.3...
ABSTRACT Transiting exoplanets orbiting young nearby stars are ideal laboratories for testing theories of planet formation and evolution. However, to date only a handful with age &lt;1 Gyr have been found host transiting exoplanets. Here we present the discovery validation sub-Neptune around HD 18599 , (300 Myr), (d = 40 pc) K star. We validate candidate as bona fide using data from TESS Spitzer Gaia missions, ground-based photometry IRSF LCO PEST NGTS speckle imaging Gemini,...
We present combined $\approx 14-37~\rm ks$ Chandra observations of seven $z = 1.6-2.7$ broad absorption line (BAL) quasars selected from the Large Bright Quasar Survey (LBQS). These objects are high-ionization BAL (HiBAL) quasars, and they were undetected in hard band ($2-8$ keV) previous observations. The stacking analyses suggested that these likely contain some candidates for intrinsically X-ray weak quasars. With new observations, six targets detected. calculate their effective power-law...
Abstract We report the discovery of an extreme X-ray flux rise (by a factor ≳20) weak-line quasar Sloan Digital Sky Survey (SDSS) J153913.47+395423.4 (hereafter SDSS J1539+3954) at z = 1.935. J1539+3954 is most-luminous object among radio-quiet type 1 active galactic nuclei (AGNs) where such dramatic variability has been observed. Before rise, appeared weak compared with expectation from its ultraviolet (UV) flux; after ratio and UV consistent majority AGN population. also present...
The progressively dominant role of software in safety-critical systems raise concerns about the dependability. There are limited mature practices and guides for assessing dependability analyzing system-level hazards triggered by anomalies. A problem is that faults, errors, failures represent anomalies, albeit with different natures, usually used indistinctly to predict dependability, leading unsolid results. lack such consensual conceptualization also leads poor interoperability between...
We investigate systematically the X-ray emission from type 1 quasars using a sample of 1825 Sloan Digital Sky Survey (SDSS) non-broad absorption line (non-BAL) with Chandra archival observations. A significant correlation is found between X-ray-to-optical power-law slope parameter ($\alpha_{\rm OX}$) and 2500 $\r{A}$ monochromatic luminosity ($L_{\rm 2500~\r{A}}$), weakness quasar assessed via deviation its $\alpha_{\rm OX}$ value that expected this relation. demonstrate existence population...
We report strong and rapid X-ray variability found from the super-Eddington accreting quasar SDSS J081456.10+532533.5 at $z=0.1197$. It has a black-hole mass of $2.7\times10^{7}{M_{\odot}}$ dimensionless accretion rate $\approx4$ measured reverberation-mapping observations. showed weak emission in 2021 February Chandra observation, with 2 keV flux density being $9.6^{+11.6}_{-4.6}$ times lower compared to an archival Swift observation. The is also $11.7^{+9.6}_{-6.3}$ weaker expectation its...
This paper presents an overview of design for dependability as a process involving three distinct but interrelated activities: risk analysis, mitigation, and assessment. Although these activities have been the subject numerous works, few them address issue their integration into rigorous flows. Moreover, most existing results focus on small-size safety-critical systems with specific static architectures. They cannot be applied to large systems, such autonomous dynamic heterogeneous...
Previous studies suggest that the combination of model-based fault injection and model checking can effectively detect dependability bottlenecks verify fault-tolerance capability systems at very early phases their lifecycles. However, a challenge applying such techniques in industry is semi-formal modeling languages like UML cannot easily support automated analysis formal verification. To address this challenge, we propose verification framework based on sequence diagrams. The idea to create...
We utilize recent NuSTAR observations (co-added depth $\approx55$-120 ks) of PG $1001+054$, $1254+047$, and PHL 1811 to constrain their hard X-ray ($\gtrsim5$ keV) weakness spectral shapes, thus investigate the nature extreme weakness. These quasars showed very weak soft emission, they were proposed be intrinsically weak, with coronae producing continuum emission relative optical/UV emission. However, new suggest an alternative explanation. The 3-24 keV shapes for $1001+054$ are likely flat...