Photopolarimetric observations of the BL Lac object PKS 2155-304
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Many quasi‐simultaneous optical observations of four BL Lac objects were obtained at the Yunnan and Shanghai Observatories. In this paper, data for the optical spectral index of four BL Lac objects are presented. Our results show that the optical spectral index of these BL Lac objects is characterized by variability. The optical spectra of the BL Lac objects H0323+022 and ON 231 flatten when the sources brighten, whereas they steepen for the objects S5 0716+71 and OJ 287.
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view Abstract Citations (37) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An Optical Polarization Survey for BL Lacertae Objects and Highly Polarized Quasars Jannuzi, Buell T. ; Green, Richard F. ; French, Howard Abstract We present the results of an extensive optical survey for highly polarized objects. The survey is complete to a B magnitude of 20 and covers 560 square degrees. We did not find any confirmed BL Lac objects, highly polarized quasars, or blazars, but we are able to constrain the surface density of the various populations of linearly polarized objects. Our constraints on the numbers of a population of polarized objects are a function of the duty cycle and the degree of polarization of the objects being constrained. We rule out the presence of an abundant population of radio-quiet BL Lacertae objects. Publication: The Astrophysical Journal Pub Date: February 1993 DOI: 10.1086/172262 Bibcode: 1993ApJ...404..100J Keywords: Active Galactic Nuclei; Bl Lacertae Objects; Optical Polarization; Quasars; Sky Surveys (Astronomy); Astronomical Photography; Astronomical Photometry; Monte Carlo Method; Schmidt Telescopes; X Ray Astronomy; Astrophysics; GALAXIES: BL LACERTAE OBJECTS: GENERAL; POLARIZATION full text sources ADS | data products SIMBAD (2) NED (2)
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On the basis of results of optical photometry and polarimetry of OJ287 and Mrk421 since 1981, we find two states of activities for both objects. In OJ287, a color-magnitude relation which is consistent with the standard jet-shock model is seen after the outburst in 1983, while before 1982 the optical colors were almost constant. In Mrk421, the colors became redder in 1985–87, and the change of the preferred direction of polarization was associated on smaller time scale in 1987.
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