Quasars| Quasars |
In General > s.a. black holes [alternatives]; black
hole phenomenology and types.
* Idea: Objects characterized
by pointlike appearance (almost stellar, earlier called quasi-stellar objects
or QSO's) and large redshifts (peaking
at z 
2).
* Nature: They are almost certainly brilliant luminous cores of galaxies,
powered by infalling matter.
* Evidence: Other galaxies have similar central engines, with a wide
range of luminosities, and all quasars within z 0.7
show a faint fuzzy nebulosity,
which often resembles a normal galaxy in appearance and spectrum.
* Energy source: Cannot
be just nuclear reactions, and the most attractive possibility is the presence
of large ( 10
MSun) black holes, with matter falling
into them and converting up to 50% of its mass into
radiation.
* Interactions: The fraction
of them in interaction with other galaxies is far greater than the corresponding
fraction for all galaxies; This indicates
that the presence of a quasar nucleus is strongly related to the
interaction with another galaxy; The mechanism could be that if there is
already
a compact massive nucleus, matter coming from the other, smaller galaxy
could
be funneled into it.
* Puzzle: 1996, Some
quasars seem to be (visually) associated with other galaxies, but have a very
different
redshift; No good explanation has been found yet.
References
@ General, reviews: Weedman 86 [III]; Rech(92)oct, p1118; Disney SA(98)jun;
Osmer ap/99-in;
Lacy ap/06.
@ Unconventional redshift interpretation: Arp et al ap/05 [periodicities];
Arp a0711 [evolving
intrinsic redshift]; Hartnett a0712 [periodicities].
@ Other unconventional: Moret-Bailly ap/03, ap/04 [as
neutron stars!].
Microquasars
* Idea: Galactic miniatures
of the far more distant quasars, obtained when accreting neutron stars eject
relativistic particles orthogonal to the accretion disk, instead of confining
disk-material down to the magnetic poles and creating the two emitting caps
typical for a X-ray pulsar.
@ Reviews: Ribo ap/04-in;
Massi Hab(05)ap,
ap/06-in;
Mirabel ap/07-in.
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11 jun 2008