585 research outputs found
Repeated Relativistic Ejections in GRS 1915+105
In 1994 February-August we observed with the VLA four ejection events of
radio emitting clouds from the high energy source GRS 1915+105. These events
are all consistent with anti-parallel ejections of twin pairs of clouds moving
away from the compact source at 0.92 of the speed of light and angles of
70 with respect to the line of sight. The flux ratios and time
evolution of the expelled clouds are consistent with actual motions of the
radiating matter rather than with the simple propagation of pulses in a medium
moving at slower velocities. The large kinetic power of the sudden, short, and
rather discontinuous ejections exceeds by more than an order of magnitude the
maximum steady photon luminosity of the source, suggesting that in GRS 1915+105
a radiation acceleration mechanism of the ejecta is unlikely. As in other
galactic and extragalactic radio sources, the decrease in flux density as a
function of angular separation from the central source shows a steepening with
distance. Additional ejection events have been observed in 1995 and 1997 and we
compare them with the 1994 events.Comment: 20 pages, 7 figures. To appear in The Astrophysical Journal, January
10, 1999 issu
Jets from black hole binaries and Galactic Nuclei
Relativistic outflows are a common phenomenon in accreting black holes.
Despite the enormous differences in scale, stellar-mass black holes in binaries
and supermassive black holes in Galactic Nuclei produce jets with analogous
properties. In both are observed two types of relativistic outflows: 1) steady
compact jets with flat-spectrum, and 2) sporadic extended jets with
steep-spectrum and apparent superluminal motions. Besides, the most common
class of gamma-ray bursts are afterglows from ultra-relativistic jets
associated to the formation of black holes at cosmological distances.Comment: 6 pages, 3 figures. To be published at the Proceedings of the ESO
Workshop on Black holes in binaries and galactic nuclei. September 6-8, 1999,
Garching, German
Phenomenological Analogies in Black Hole Systems of all Masses
I review the progress made on the physics of relativistic jets from black
hole systems in the context of the analogy between AGN and microquasars that
was proposed one decade ago. If the emerging empirical correlations between the
observational properties of stellar and supermassive black holes will become
more robust, we will use them to determine the mass and spin of black holes,
independently of theoretical models. Microquasars are fossils of sources of
Gamma-ray bursts (GRBs) of long duration, and their kinematics provides
observational clues on the physics of collapsars. If jets in GRBs, microquasars
and AGN are due to a unique universal magnetohydrodynamic mechanism, synergy
between the research on these three different classes of cosmic objects will
lead to further progress in black hole physics and astrophysics.Comment: Invited review at the conference "Stellar-Mass, Intermediate-Mass,
and Supermassive Black Holes." Kyoto, 25-31 October 2003. 11 pages, 5 figures
(4 in color). To be published as Progress of Theoretical Physics, Supplemen
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