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We present Chandra X-ray (0.2-8 keV) and Very Large Array radio (15 and 5 GHz) images of the $gamma$-ray bright, superluminal quasar 0827+243. The X-ray jet bends sharply--by ~90 deg., presumably amplified by projection effects--5 from the core. Only extremely weak radio emission is detected between the nuclear region and the bend. The X-ray continuum spectrum of the combined emission of the knots is rather flat, with a slope of $-0.4pm 0.2$, while the 5-15 GHz spectra are steeper for knots detected in the radio. These characteristics, as well as non-detection of the jet in the optical band by the Hubble Space Telescope, pose challenges to models for the spectral energy distributions (SEDs) of the jet features. The SEDs could arise from pure synchrotron emission from either a single or dual population of relativistic electrons only if the minimum electron energy per unit mass $gamma_{min} gtrsim 1000$. Alternatively, the X-ray emission could result from inverse Compton scattering of the Cosmic Microwave Background photons by electrons with Lorentz factors as low as $gamma sim 15$. In all models, the bulk Lorentz factor of the jet flow $Gammagtrsim 20$ found on parsec scales must continue without substantial deceleration out to 800 kpc (deprojected) from the nucleus. Deceleration does appear to occur at and beyond the sharp bend, such that the flow could be only mildly relativistic at the end of the jet.
The quasar 3C~286 is one of two compact steep spectrum sources detected by the {it Fermi}/LAT. Here, we investigate the radio properties of the parsec(pc)-scale jet and its (possible) association with the $gamma$-ray emission in 3C~286. The Very Long
Centaurus A (Cen~A) is the nearest active radio galaxy, which has kiloparsec (kpc) scale jets and {giant lobes detected by various instruments in radio and X-ray frequency ranges}. The $Fermi$--Large Area Telescope and High Energy Stereoscopic System
The gravitational wave (GW) memory from a radiating and decelerating point mass is studied in detail. It is found that for isotropic photon emission the memory generated from the photons is essentially the same with the memory from the point mass tha
We analyze total and polarized intensity images of the quasar 3C 454.3 obtained monthly with the VLBA at 43 GHz within the ongoing Boston U. monitoring program of gamma-ray blazars started in June 2007. The data are supplemented by VLBA observations
We analyze the multifrequency behavior of the quasar 3C 454.3 during three prominent gamma-ray outbursts: 2009 Autumn, 2010 Spring, and 2010 Autumn. The data reveal a repeating pattern, including a triple flare structure, in the properties of each ga