Dual - Frequency VSOP Observations of AO 0235 + 164
نویسندگان
چکیده
AO 0235+164 is a very compact, flat spectrum radio source identified as a BL Lac object at a redshift of z = 0.94. It is one of the most violently variable extragalactic objects at both optical and radio wavelengths. The radio structure of the source revealed by various ground-based VLBI observations is dominated by a nearly unresolved compact component at almost all available frequencies. Dual-frequency space VLBI observations of AO 0235+164 were made with the VSOP mission in JanuaryFebruary 1999. The array of the Japanese HALCA satellite and co-observing ground radio telescopes in Australia, Japan, China and South Africa allowed us to study AO 0235+164 with an unprecedented angular resolution at frequencies of 1.6 and 5 GHz. We report on the sub-milliarcsecond structural properties of the source. The 5-GHz observations led to an estimate of TB > 5.8× 10 13 K for the rest-frame brightness temperature of the core, which is the highest value measured with VSOP to date.
منابع مشابه
VSOP Monitoring of the Compact BL Lac Object AO 0235 + 164 Sándor
In 1999, the highly compact and variable BL Lac object AO 0235+164 was identified as the highest brightness temperature active galactic nucleus observed with the VLBI Space Observatory Programme (VSOP), with TB > 5.8× 1013K (Frey et al. 2000). The sub-milliarcsec radio structure of this source has been studied with dualfrequency (1.6 and 5GHz), polarization-sensitive VSOP observations during 20...
متن کاملHarmonic QPOs and Thick Accretion Disk Oscillations in BL Lac Object AO 0235 + 164
Periodic outbursts are observed in many AGNs and usually explained with a supermassive black hole binary (SMBHB) scenario. However, multiple periods are observed in some AGNs and cannot be explained with it. Here we analyze the periodicity of the radio light curves of AO 0235+164 at multi-frequencies and report the discovery of six QPOs in integer ratio 1:2:3:4:5:6 of QPO frequencies, of which ...
متن کاملUnusual radio variability in the BL Lacertae object 0235 + 164
We present radio observations at three frequencies and contemporaneous optical monitoring of the peculiar BL Lac object AO 0235+164. During a three-week campaign with the VLA we observed intraday variability in this source and found a distinct peak which can be identified throughout the radio frequencies and tentatively connected to the R-band variations. This event is characterized by unusual ...
متن کاملOptical Intra-day Variability in Blazars
We selected a sample of a dozen blazars which are the prime candidates for simultaneous multi-wavelength observing campaigns in their outburst phase. We searched for optical outbursts, intra-day variability and short term variability in these blazars. We carried out optical photometric monitoring of nine of these blazars in 13 observing nights during our observing run October 27, 2006 − March 2...
متن کاملExtreme intranight variability in the BL Lacertae object AO 0235 + 164
We present results of two-colour photometry with high time resolution of the violently variable BL Lac object AO 0235+164. We have found extreme intranight variability with amplitudes of ∼ 100% over time scales of 24 hours. Changes of 0.5 magnitudes in both R and V bands were measured within a single night, and variations up to 1.2 magnitudes occurred from night to night. A complete outburst wi...
متن کامل