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First Simultaneous UBVRI Photopolarimetric Observations of a Sample of Normal Quasars

from II - Luminosity Functions and Continuum Energy Distributions

Published online by Cambridge University Press:  04 August 2010

L.O. Takalo
Affiliation:
University of Turku, Tuorla Observatory, Tuorla, SF-21500 Piikkiö, Finland
A. Sillanpää
Affiliation:
University of Turku, Tuorla Observatory, Tuorla, SF-21500 Piikkiö, Finland
M.R. Kidger
Affiliation:
Instituto de Astroficica de Canarias, 38200 La Laguna, Tenerife, Spain
J.A. de Diego
Affiliation:
Instituto de Astroficica de Canarias, 38200 La Laguna, Tenerife, Spain
Andrew Robinson
Affiliation:
University of Cambridge
Roberto Juan Terlevich
Affiliation:
Royal Greenwich Observatory, Cambridge
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Summary

Abstract

We present the results from truly simultaneous UBVRI photopolarimetric observations on “normal” quasars at the Nordic Optical Telescope. Some of the observed quasars show no measurable polarization, this being consistent with previous measurements of these objects. On the other hand in PG 1008+133 and PG 1351+64 we detected low (1.5%) polarization. In PG1351+64 this polarization shows also wavelength dependence and in PG 1008+133 the position angle show wavelength dependence. These are the first such observations in these quasars.

Observations

We have selected quasars from the Veron-Cetty & Veron (1991) catalogue. The only selection criteria being: the object is bright enough to be observed in reasonable integration time. In practice this means that Vmag < 16. And that the object can be observed from La Palma, using the Nordic Optical Telescope (Declination > −30°).

The observations were made at the Nordic Optical Telescope during February 1991 and July 1992. We used the Turku photopolarimeter. This instrument gives truly simultaneous results in five (UBVRI) colour bands. A detailed description of the instrument and the observing method can be found from Takalo et al. (1992, and references therein). The total integration time depended on the object brightness, ranging from one to four hours.

Results

The main results are listed in Table 1., where we list the observed objects according to the measured polarization.

Type
Chapter
Information
The Nature of Compact Objects in Active Galactic Nuclei
Proceedings of the 33rd Herstmonceux Conference, held in Cambridge, July 6-22, 1992
, pp. 147 - 149
Publisher: Cambridge University Press
Print publication year: 1994

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