AO 0235+164 is shown to be in a flaring state.[8][9] It also had two major outbursts in 1975 and 1987.[10] Another outburst occurred in 1997 the duration of which was on the order of 800 days with a maximumluminosity of 9.86 x 1047 erg s−1 suggesting amicrolensing event scenario.[11]
During aFermi Large Area Telescope multi-wavelength observation between August 2008 and February 2009, the blazar underwent a high state showing intensegamma ray activity before falling to a low state.[12] It displayednear-infrared flares in 2014 and 2017.[13][14] By 2020, AO 0235+164 had brightened again, displaying an opticalflare that reached its peak in 2021. However, when compared to previous flares, it is shown weaker despiteemission at all wavelengths increasing from gamma rays tomillimeter waves and its light curve exhibiting a multi-peak structure with sharp variability at highenergies.[15]
The opticalbrightness of AO 0235+164 is known to vary across differenttime scales ranging from a few hours inoptical to a long period of time in radio.[16] During the last three nights in January 2024, its brightness level significantly increased rapidly over 2magnitudes in the R-band.[17]
The source of AO 0235+164 is substantially resolved, however no structural position angle is distinguished .[18] Additionally AO 0235+165 also contains a compact core with a weak extended structure located north-northwest from it, indicating a result of a smallviewing angle found for the source.[16] A component can be seen 0.7 mas away from the core with aposition angle of = 7°.[19] The radio components also havesuperluminal velocities reaching as fast as β ~ 30h−1 (h = H/100 km Mpc−1 s−1).[20]
AO 0235+164 contains asupermassive black hole in its center. Based on analysis of a broadmagnesiumspectral line in its spectrum, the mass is 7.9 x 107Mʘ.[21] Alternatively, it might also contain a closebinary black hole system with estimated similar masses of order of 1010 Mʘ withvelocities of 104 and 5 x 103 kilometers per seconds.[22]
^Raiteri, C. M.; Villata, M.; Kadler, M.; Ibrahimov, M. A.; Kurtanidze, O. M.; Larionov, V. M. (December 2006). "Multifrequency variability of the blazar AO 0235+164. The WEBT campaign in 2004-2005 and long-term SED analysis".Astronomy & Astrophysics.459 (3):731–743.arXiv:astro-ph/0608627.doi:10.1051/0004-6361:20065744.ISSN0004-6361.
