Relativistic jets and accretion phenomena associated with galactic and extragalactic black holes

• Autor(a) principal: Gouveia Dal Pino,E. M. de
• Data de Publicação: 2005
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Brazilian Journal of Physics
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-97332005000700043

More than a dozen binary star systems hosting stellar-mass black holes have been discovered in our galaxy. Some of them eject collimated relativistic jets with apparent velocities larger than the light speed. These objects have been named microquasars thanks to their similarity with the distant quasars or active nuclei of galaxies that host supermassive black holes. We have recently proposed that the large scale superluminal ejections observed in the microquasars (e.g., GRS 1915+105 source) during radio flare events are produced by violent magnetic reconnection episodes in the accretion disk that surrounds the central source, a ten-solar-mass black hole (de Gouveia Dal Pino and Lazarian 2005). The process occurs when a large-scale magnetic field is established by a turbulent dynamo in the inner disk region with a ratio between the gas+radiation and the magnetic pressures beta ~ 1. During this process, substantial angular momentum is removed from the disk by the wind generated by the vertical magnetic flux therefore increasing the disk mass accretion to a value near (but below) the critical Eddington limit. Part of the magnetic energy released by reconnection heats the coronal gas above the disk that produces a steep, soft X-ray spectrum with luminosity consistent with observations. The remaining magnetic energy released goes to accelerate the particles to relativistic velocities (v ~ vA ~ c, where vA is the Alfvén speed) in the reconnection site through first-order Fermi processes. For the first time we have examined the Fermi process within the reconnection zone and found that a power-law electron distribution is produced N(E) <FONT FACE=Symbol>µ</FONT> E-alphaE, with alphaE = 5/2, and a corresponding synchrotron radio power-law spectrum with a spectral index which is compatible with that observed during the flares (Snu <FONT FACE=Symbol>µ n</FONT>-0.75), though a standard Fermi process behind shocks that develop just above the reconnection site is also possible. The possibility that the ejection mechanism of relativistic blobs induced by magnetic reconnection can be applied to all classes of black hole-relativisitc jet systems, from microquasars to quasars and active galactic nuclei, is addressed here.