Special Relativity at Action in the Universe

Abstract

Nature succeeds in accelerating extended and massive objects to relativistic velocities. Jets in Active Galactic Nuclei and in galactic superluminal sources and gamma-ray bursts fireballs have bulk Lorentz factors from a few to several hundreds. A variety of effects then arises, such as the beaming of the produced radiation, light aberration, time contraction and the Doppler frequency shift. I will emphasize that special relativity applied to real (i.e. extended) observed objects inevitably must take into account that any piece of information is carried by photons. Being created in different parts of the source, they travel different paths to reach the observer, depending on the viewing angle. The object is seen rotated, not contracted, and at small viewing angles time intervals are observed shorter than intrinsic ones.

Constraining the intrinsic energy of GRB events

“…However, it is assumed that the radiation is emitted from a source which is moving highly relativistically (fireball/relativistic blast wave model). Then, in concordance with that exposed by others authors (see e.g., [4,9]), the observed radiation must be affected by the boosting Lorentz factor δ. Consequently, we would to detect in the laboratory frame a flux F enhanced by the δ factor (F = δ 4 F ′ ), and at the observed frame we should expect an anisotropic flux which is dependent on the propagation direction of radiation (F = F (r, θ, φ)).…”

“…Several authors have made evident the fact that the energy released in a gamma-ray event could be overestimated if the emission is considered isotropic (see e.g., [3,4]). In these models the energy involved is extremely large leading to powers of about 10 52 ergs sec -10 54 ergs sec in a single event.…”

Insights into the emission of the blazar 1ES 1011+496 through unprecedented broadband observations during 2011 and 2012

“…Out of the 45 known TeV HBLs 19 , 13 have been targets of VLBA measurements (Lister et al 2013;Piner & Edwards 2013;Tiet et al 2012;Piner et al 2010). The majority of these HBLs show rather low apparent speeds, i.e., < 1 c. In addition to 1ES 1011+496, a superluminal motion (e.g., Urry & Padovani 1995;Ghisellini 2000) of 1.2 ± 0.4 c (Piner et al 2010) was measured for the HBL H 1426+428 with a statistical significance of ≥ 2 σ. Given the statistical error, the apparent speed of this motion could also be < 1 c, which makes 1ES 1011+496 the HBL with the highest statistically significant superluminal speed measured so far.…”

“…Blazars are a subclass of radio-loud active galactic nuclei (AGNs) with their relativistic particle jets closely aligned to the line of sight of the observer. They are highly variable at nearly all wavelengths at various timescales, and their emission is dominated by a non-thermal continuum spanning from radio to VHE γ rays which is assumed to be produced within the jets and boosted by beaming (e.g., Urry & Padovani 1995;Ghisellini 2000). The spectral energy distribution (SED) of blazars shows two distinct broad components: a low-energy bump in the optical to X-ray range that is commonly associated with synchrotron emission of electrons and a high-energy bump in the γ-ray band.…”

Apparent superluminal velocities and random walk in the velocity space

“…The basic idea behind the apparent superluminal motion is rather elementary: this effect arises from the Doppler contraction of the arrival times of photons due to the finite speed of light [6,7]. This Doppler contraction is most easily explained by the space-time diagram in Fig.…”