Superluminal jets in astrophysics : kinematics and X-ray emission

Other Title(s)

دراسة النفاثات الأسرع من الضوء : آليتها الحركية و آلية اصدار الأشعة السينية الفلكية

University

Al albayt University

Faculty

Faculty of Sciences

Department

Department of Physics

University Country

Jordan

Degree

Master

Degree Date

2009

English Abstract

Superluminal motion is a term used to describe rapid systematic changes in the appearance of an astronomical object with an observed speed that appears to be faster than the speed of light; it may reach more than 10c.

This phenomenon was first recognized in the early1970s, although the possibility of very high apparent expansion speeds was reorganized much earlier.

It is observed in radio wavelengths of quasars and galaxies.

In the 1990s, rapid motions have also been discovered in a few objects within our own galaxy, and the first optical detection of superluminal motion in an extragalactic source has also been obtained.

At first these superluminal motions provoked concern because they appeared to violate the postulates of special theory of relativity, but they were soon interpreted as illusions due to relativistic aberration, and the ultimate physical interpretation had remained uncertain.

However, several models for such phenomena were developed; the majority of these explanations are based on the beaming model, which involves the relativistic aberration of a very fast blob moving nearly toward us.

Whereas some other observations find a natural explanation in relativistic expansion, this simple model has faced some difficulties such as the non-existence of beamed components in some of the superluminal celestial objects.

But the exact nature of these very fast blobs is not yet clear.

In this thesis, a new model has been viewed without the violation of the postulates of special theory of relativity.

The model describes the interaction of such jets that emerge from compact objects, and it attributes the superluminal speed as a result of the interaction between high speed jets and the surrounding medium, so the speed of this interaction represents superluminal speed.

Note that, all previous studies relevant to superluminal sources found an interaction in ejected matter from compact objects and the material surrounding the sources.

X-ray binary system transient sources GRS 1915+105, GRO J1655-40, XTE J1550-564 and XTE J1784-288 show high variability of X-ray spectra and exhibit multi-wavelength bands of spectra and superluminal speeds.

All of these sources have jets that collide with environmental material, being decelerated while brightening at the leading edge of the jet.

On the other hand, the superluminal jets in GRS 1915+105 are due to the internal shock that forms when the oscillation or discrete baby jet (compact jet) catches up and interacts with the previously generated slowly moving wind from the accretion disk.

According to the same observations, astrophysicists show that the absence of superluminal jets in GRS 1915+105 is attributed to the absence of the wind.

In addition, the superluminal motion corresponds to the strength of the wind.

We thus conclude that our model applied to superluminal motion in micro quasars shows high compatibility of many observations of such sources with Sabat assumption.