Evolution of relativistic jets from XTE J1550-564and the environment of microquasars

摘要

Two relativistic X-ray jets have been detected with the Chandra X-ray observatory inthe black hole X-ray transient XTE J1550-564. We report a full analysis of the evolution of the twojets with a gamma-ray burst external shock model. A plausible scenario suggests a cavity outsidethe central source and the jets first travelled with constant velocity and then are slowed down bythe interactions between the jets and the interstellar medium (ISM). The best fitted radius of thecavity is —0.36 pc on the eastern side and ~0.46 pc on the western side, and the densities also showasymmetry, of ~0.015 cm~(-3)on the east to ~0.21 cm~(-west. Large scale low density regionis also found in another microquasar system, H 1743-322. These results are consistent with previoussuggestions that the environment of microquasars should be rather vacuous, compared to the normalGalactic environment A generic scenario for microquasar jets is proposed, classifying the observedjets into three main categories, with different jet morphologies (and sizes) corresponding to differentscales of vacuous environments surrounding them.