Bibcode
de Diego, Jose A.; Gonzalez-Perez, Jose N.; Charles, Phil; Kidger, Mark
Referencia bibliográfica
American Astronomical Society, 184th AAS Meeting, #17.07; Bulletin of the American Astronomical Society, Vol. 26, p.885
Fecha de publicación:
5
1994
Número de citas
1
Número de citas referidas
1
Descripción
The BL Lac object OJ287 has been studied with the 4.2m William Herschel
Telescope (WHT) from the Spanish Observatory of La Palma on six nights
in December 1993 and January 1994, as part of the OJ-94 International
Campaign of monitoring of OJ287. At the time of the first observations,
in mid-December the object was in the decline phase of a moderate
outburst, reaching minimum in early January. In order to get both
spectral and polarimetric observations, we used the ISIS double
spectropolarimeter, giving us a spectral resolution of 3 Angstroms over
the range from 5500-9000 Angstroms. This permits both the rapid
continuum polarisation variations to be examined from individual
exposures (resolution 40 minutes, provided by four individual
integrations with different positions of the calcite retarder) and , by
summing all the exposures of a full night (a total integration time of
up to 8 hours), the weak emission lines may be studied at a resolution
far higher than has ever previously been possible. A period or
pseudoperiod of 11.65 yr has been claimed for the outbursts of this
object (Sillapaa et al 1988, Kidger et al 1992), which has been
interpreted as due to a binary black hole (Sillapaa et al 1988). This
model predicts an outburst at some time in 1994. If the Winter 1993-94
eruption corresponds to the expected 1994 outburst, the rise in
brightness would be associated to accretion processes and, therefore, we
hope to find a polarized spectrum different of those originated by
synchrotron sources. The WHT observations are, we believe, the first of
their kind of a blazar and these data will help to elucidate this
question, apart from supplying valuable information on the emission
processes in active galactic nuclei. References: Sillanpaa A., Haarala
S., Valtonen M., Sundelius B., Byrd G.G, 1988, ApJ, 325, 628 Kidger M.,
Takalo L., Sillanpaa A., 1992, A&A, 264, 32