Polarisation variability of OJ287 in 1993/94

Session 94 -- Acceleration and Jets in AGN, High Redshift Quasars, Polarization
Oral presentation, Wednesday, 11, 1995, 2:00pm - 3:30pm

[94.05] Polarisation variability of OJ287 in 1993/94

J.-M. Rodr\'\i guez-Espinosa, M. Kidger (Instituto de Astrof\'\i sica de Canarias, La Laguna, 38200 Tenerife, Spain ), D. Wills ( University of Texas, Austin, TX, USA), J.A. de Diego, J.N. Gonz\'alez-P\'erez (Instituto de Astrof\'\i sica de Canarias, La Laguna, 38200 Tenerife, Spain ), A. Sillanp\"a\"a, L.O. Takalo , T. Pursimo , H. Lehto , K. Nilsson (Tuorla Observatory, Tuorla 21500 Piikki\"o, Finland ), Yu.S. Efimov, N. Shakhovskoy (Crimean Astrophysical Observatory, P/O Naunchny, 334413 Crimea, Ukraine ), P. A. Charles ( University of Oxford, dept. of Astrophysics, Nuclear$\&$Astrophysics Laboratory, Keble Road Oxford, OX1 3RH, England)

The polarization of OJ287 was observed during the 1993/94 observing campaign within the OJ-94 international collaboration. Data were taken, usually in UBVRI, at various epochs from November 1993 to May 1994. The polarization degree varied from $\sim$1\% to 18\%, although was generally from 5-10\%. During the observing season the visible flux increased by a factor of four approximately, but no dilution of the polarization degree is seen, indicating that the total polarised flux increased with the unpolarised flux. A pronounced rotation is seen though in the polarization vector during the observing campaign, which may be correlated with the flux changes. Polarisation measurements were made on a series of nights in January 1994, coincident with a sharp 1 magnitude flare in the visible. Large position angle variations were seen during the flare, which appear to correlate with the visible flux. The polarization degree also dropped to a low, but quite constant, level at this time. We will discuss these variations in terms of models of the polarization emission mechanism.

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