Bibcode
Takalo, L. O.; Kidger, M.; de Diego, J. A.; Sillanpaa, A.
Bibliographical reference
American Astronomical Society, 181st AAS Meeting, #35.10; Bulletin of the American Astronomical Society, Vol. 24, p.1173
Advertised on:
12
1992
Citations
0
Refereed citations
0
Description
We have observed a sample of "ordinary" quasars, selected only on the
grounds of their relative brightness in the visible, with the Turku
Photopolarimeter on the 2.56m Nordic Optical Telescope, on La Palma,
Canary Islands. The instrument permits us to obtain simultaneous UBVRI
photometry and polarimetry of objects down to 16th magnitude, with the
errors in the range <0.2-0.5%. Here we report results for an initial
sample of sixteen objects, several of which have more than one
observation. Our aim is to produce a sample of at least fifty objects
which will allow us to examine the statistical properties of the
polarization of ordinary quasars. Whilst our sample is still small for
meaninful statistical analysis, various interesting trends are emerging.
We find that, of 16 objects, 9 are detected at the 3 sigma level in at
least two bands, all but one of which are radio quiet (ie: QSOs), whilst
only one radio loud quasar (QSS) is detected. We also find that 7 of the
quasars with detectable polarization are X-ray loud, whereas, of the
non-detected quasars, 5 out of 7 are X-ray quiet and the same proportion
are radio loud. Various objects show frequency dependence either of
polarization degree, or position angle. Some evidence exists that nearly
half of the sample may possibly have a polarization which varies by a
factor of two in time scales of years.