2018/01/13 by Zhi-Bin Zhang, Zhang, Zhi-Bin
Physics and Astronomy · #Astronomy and Astrophysical Research #FOS: Physical sciences #Gamma-ray bursts and supernovae #High Energy Astrophysical Phenomena (astro-ph.HE) #Pulsars and Gravitational Waves Research
paper · pdf · doi:10.48550/arxiv.1801.04374
openalex publication_date 2018/01/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Superluminal motion has been found to occur in many kinds of celestial bodies with the relativistic ejecta, especially for some active galactic nuclei (AGNs), gamma-ray bursts (GRBs) and micro-quasars, although these objects are largely different in their lifetimes, sizes and features. We compare the apparent superluminal motions of GRBs with AGNs and different sub-classes of AGNs (e.g., Radio galaxies, BL Lac objects, and Quasars). Particularly, we focus on two low luminosity GRBs, namely 060218 and 170817A, that are ultra-long and short bursts associated with supernova and gravitational wave, respectively. The apparent transverse velocity (βapp) of Swift and pre-Swift GRBs are tightly correlated with the Doppler factor δ as βapp∝δ0.5, while all AGNs distribute around the line of βapp= δ behaving a weak correlation of βapp with δ . In contrast, βapp is positively correlated with Lorenz factor γ or γ2(1+z)-1, not for GRBs but for AGNs. βapp and 1+z are independent for neither GRBs nor AGNs, but apparently exhibit a positive correlation of βapp with 1+z from AGNs to GRBs, showing a cosmological effect of evolution with redshift. I also found that GRB 170817A and GRB 060218 are outliers of the above correlations. Superluminal properties of GRBs are significantly different from those of AGNs. However, there are no obvious differences between radio galaxies, BL Lac objects, and quasars in terms of their superluminal motion. In despite of radiation mechanism, beaming effect and cosmological expanding would play the same roles on the superluminal motion for AGNs and GRBs.