Optical and radio variability of the BL Lacertae object AO 0235+16: A possible 5-6 year periodicity

By C. Raiteri, M. Villata, H. Aller, M. Aller, J. Heidt, O. Kurtanidze, L. Lanteri, M. Maesano, Enrico Massaro, F. Montagni and 26 more. 2001

148 citations recorded by the source corpus.

The BL Lacertae object AO 0235+16 is well known for its extreme optical and radio variability. New optical and radio data have been collected in the last four years by a wide international collaboration, which conrm the intense activity of this source: on the long term, overall variations of 5 mag in the R band and up to a factor 18 in the radio fluxes were detected, while short-term variability up to 0:5 mag in a few hours and 1: 3m ag in one day was observed in the optical band. The optical data also include the results of the Whole Earth Blazar Telescope (WEBT) rst-light campaign organized in November 1997, involving a dozen optical observatories. The optical spectrum is observed to basically steepen when the source gets fainter. We have investigated the existence of typical variability time scales and of possible correlations between the optical and radio emissions by means of visual inspection and Discrete Correlation Function (DCF) analysis. On the long term, the autocorrelation function of the optical data shows a double-peaked maximum at 4100{4200 days (11:2{11:5 years), while a double-peaked maximum at 3900{4200 days (10:7{11:5 years) is visible in the radio autocorrelation functions. The existence of this similar characteristic time scale of variability in the two bands is by itself an indication of optical-radio correlation. A further analysis by means of Discrete Fourier Transform (DFT) technique and folded light curves reveals that the major radio outbursts repeat quasi-regularly with a periodicity of5:7 years, i.e. half the above time scale. This period is also in agreement with the occurrence of some of the major optical outbursts, but not all of them. Visual inspection and DCF analysis of the optical and radio light curves then reveal that in some cases optical outbursts seem to be simultaneous with radio ones, but in other cases they lead the radio events. Moreover, a deep inspection of the radio light curves suggests that in at least two occasions (the 1992{1993 and 1998 outbursts) flux variations at the higher frequencies may have led those at the lower ones.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/b149f0c7d62614c3962a522e8fa44cfa25a134f8

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Citations in the corpus

Optical and radio behaviour of the BL Lacertae object 0716+714 ⋆ (2003, unknown): “…OJ 287 optical light curve (Sillanpää et al. 1988, 1996; Villata et al. 1998b), the ∼7.8 year period discovered in the optical light curve of BL Lacertae (Smith & Nair 1995; Marchenko et al. 1996), and the ∼5.7 year period recognized in the radio light curves of AO 0235+16 (Raiteri et al. 2001).”
Photopolarimetric Monitoring of Blazars in the Optical and Near-Infrared Bands with the Kanata Telescope. I. Correlations between Flux, Color, and Polarization (2011, unknown): “Raiteri et al. (2001) performed multi-band photometric observations of AO 0235+164 for four years, and found a bluer-whenbrighter trend.”
Massive Black Hole Binary Evolution (2004, unknown): “7 [180] 3C 66A 0.”
Multi-colour optical monitoring of eight red blazars (2006, result): “However, this result is opposite to the common colour change tendency in blazars, that the spectrum becomes flatter when the source brightens (Ghisellini et al. 1997; Ghosh et al. 2000; Clements & Carini 2001; Raiteri et al. 2001; Villata et al. 2002).”
THE POPULATION OF VISCOSITY- AND GRAVITATIONAL WAVE-DRIVEN SUPERMASSIVE BLACK HOLE BINARIES AMONG LUMINOUS ACTIVE GALACTIC NUCLEI (2009, background): “…handful of blazars, whose historical light curves show periodic outbursts on timescales of a year to a decade, or even longer (see, e.g., Sillanpää et al. 1988; Liu et al. 1995, 1997; Raiteri et al. 2001; Qian et al. 2007; Tao et al. 2008, and references in these papers, for individual objects).”