Bibcode
de Diego, J. A.
Bibliographical reference
American Astronomical Society, 181st AAS Meeting, #21.02D; Bulletin of the American Astronomical Society, Vol. 24, p.1154
Advertised on:
12
1992
Citations
1
Refereed citations
1
Description
This project presents the principal conclusions of a long series of
infrared and visible observations of blazars taken from 1987-92. The
data fall broadly into three classes: spectropolarimetry in the range
4000-9500A of a small sample of selected AGNs; polarimetry of a sample
of a dozen blazars and some twenty low polarisation quasars (LPQs);
visible and infrared monitoring and fast photometry of a sample of a
dozen blazars. Representitive data are presented from each of the
observational programs. The aim is to view the AGN phenomenon and,
especially blazars, as a whole, using novel observational methods to
look for similarities and differences between distinct classes of
objects. The visible spectropolarimetric characteristics of 3C273, 3C345
and CTA102 will be discussed in detail. Observations at 8A resolution
with the 4.2m William Herschel Telescope are contrasted with existing
knowledge from broad band photopolarimetry of these objects. It is found
that the data is in broad agreement with the predictions of synchrotron
theory, but numerous problems remain. Very contrasting behavior is seen
in the polarization of the spectral lines in each object and, in 3C345
it is even found that different spectral lines within the same spectrum
show sharply different polarization characteristics. Observations of
LPQs show that at least 50% have detectable polarization, generally of
0.5-1%. The observations suggest that there are similarities between
LPQs and blazars, with good evidence of variable polarization in a
number of objects. Our initial sample of objects shows that almost all
LPQs with detectable polarization are Radio Quiet and/or x-ray loud.
Extensive fast photometry has been performed of a number of objects,
especially OJ287 (visible and infrared), Mark421 and Mark501 (infrared).
Rapid variability is found to be common, whilst simultaneous UBVRIJHK
observations show that fast spectral variability on time scales of an
hour or less also occurs with some frequency; this last has major
implications for models of the active nucleus.