Deep XMM-Newton Observations of an X-ray Weak Broad Absorption Line Quasar at z = 6.5

We report X-ray observations of the most distant known gravitationally lensed quasar, J0439+1634 at z = 6.52, which is also a broad absorption line (BAL) quasar, using the XMM-Newton Observatory. With a 130 ks exposure, the quasar is significantly detected as a point source at the optical position with a total of 358 − 19 + 19 net counts using the EPIC instrument. By fitting a power law plus Galactic absorption model to the observed spectra, we obtain a spectral slope of Γ = 1.45 − 0.09 + 0.10 . The derived optical-to-X-ray spectral slope α ox is − 2.07 − 0.01 + 0.01 , suggesting that the X-ray emission of J0439+1634 is weaker by a factor of 18 than the expectation based on its 2500 Å luminosity and the average α ox versus luminosity relationship. This is the first time that an X-ray weak BAL quasar at z > 6 has been observed spectroscopically. Its X-ray weakness is consistent with the properties of BAL quasars at lower redshift. By fitting a model including an intrinsic absorption component, we obtain intrinsic column densities of N H = 2.8 − 0.6 + 0.7 × 10 23 cm − 2 and N H = 4.3 − 1.5 + 1.8 × 10 23 cm − 2 , assuming a fixed Γ of 1.9 and a free Γ, respectively. The intrinsic rest-frame 2–10 keV luminosity is derived as (9.4–15.1) × 1043 erg s−1, after correcting for lensing magnification (μ = 51.3). The absorbed power-law model fitting indicates that J0439+1634 is the highest redshift obscured quasar with a direct measurement of the absorbing column density. The intrinsic high column density absorption can reduce the X-ray luminosity by a factor of 3–7, which also indicates that this quasar could be a candidate intrinsically X-ray weak quasar.

European VLBI Network Observations of the Proposed Dual AGN SDSS J101022.95+141300.9

During galaxy merger events, the supermassive black holes in the center of the galaxies may form a pair of active galactic nuclei (AGN) with kiloparsec-scale or even parsec-scale separation. Recently, optical observations revealed a promising dual-AGN candidate at the center of the galaxy SDSS J101022.95+141300.9 (hereafter J1010+1413). The presence of two distinct [O iii]-emitting point sources with a projected separation of ∼430 pc indicates a dual-AGN system. To search for AGN-dominated radio emission originating from the Hubble Space Telescope (HST) point sources, we carried out very long baseline interferometry observations. We resolved the radio structure of J1010+1413 and detected a single feature offset from the HST point sources and also from the Gaia optical position of the object. Our multiwavelength analysis of J1010+1413 inferred two possible interpretations of the observed properties challenging its proposed dual-AGN classification.

In-Service Detection and Quantification of Railway Wheel Flat by the Reflective Optical Position Sensor

Railway wheel tread flat is one of the main faults of railway wheels, which brings great harm to the safety of vehicle operation. In order to detect wheel flats dynamically and quantitatively when trains are running at high speed, a new wheel flat detection system based on the self-developed reflective optical position sensor is demonstrated in this paper. In this system, two sensors were mounted along each rail to measure the wheel-rail impact force of the entire circumference by detecting the displacement of the collimated laser spot. In order to establish a quantitative relationship between the sensor signal and the wheel flat length, a vehicle-track coupling dynamics analysis model was developed using the finite element method and multi-body dynamics method. The effects of train speed, load, wheel flat lengths, as well as the impact positions on impact forces were simulated and evaluated, and the measured data can be normalized according to the simulation results. The system was assessed through simulation and laboratory investigation, and real field tests were conducted to certify its validity and correctness. The system can determine the position of the flat wheel and can realize the quantification of the detected wheel flat, which has extensive application prospects.