In strong gravitational lensing, the multiple images we see correspond to light rays that leave the source in slightly different directions. If the source emission is anisotropic, the images may differ from conventional lensing predictions (which assume isotropy). To identify scales on which source anisotropy may be important, we study the angle δ between the light rays emerging from the source...

BL Lacertae objects are an extreme subclass of AGNs showing rapid and large-amplitude variability, high and variable polarization, and core-dominated radio emissions. If a strong beaming effect is the cause of the extreme observation properties, one would expect that these properties would be correlated with each other. Based on the relativistic beaming model, relationships between the polariza...

We show that a dual-population unification scheme provides a successful paradigm with which to describe the evolution and beaming of all bright extragalactic radio sources. The paradigm consists of two intrinsic radio-source populations, based on the two distinct radio-galaxy morphologies of Fanaroff-Riley classes I and II. These represent the 'unbeamed' or 'side-on' parent populations of steep...

We present radio, optical/NIR, and X-ray observations of the afterglow of the short-duration GRB 130603B, and uncover a break in the radio and optical bands at ≈ 0.5 d after the burst, best explained as a jet break with an inferred jet opening angle of ≈ 4 − 8. GRB 130603B is only the third short GRB with a radio afterglow detection to date, and the first time that a jet break is evident in the...

We propose a method to estimate the pseudo jet opening half-angle of GRBs using the spectral peak energy (Ep)–peak luminosity relation (so called Yonetoku relation) as well as the Ep–collimation-corrected γ-ray energy relation (so called Ghirlanda relation). For bursts with known jet break times and redshifts, we compared the pseudo jet opening half-angle with the standard one and found that th...

The discovery of cell-free fetal DNA (cfDNA) circulating in the maternal blood has provided new opportunities for noninvasive prenatal diagnosis (NIPD). However, the extremely low levels of cfDNA within a high background of the maternal DNA in maternal circulation necessitate highly sensitive molecular techniques for its reliable use in NIPD. In this proof of principle study, we evaluated the e...

— We examine the Swift/X-ray Telescope (XRT) light curves from the first ∼ 150 gamma-ray burst (GRB) afterglows. Although we expected to find jet breaks at typical times of 1-2 days after the GRB, we find that these appear to be extremely rare. Typical light curves have a break in the slope at about 10 4 s, followed by a single power-law decay whose slope is much too shallow to be consistent wi...