2000/07/24 by S. Frey, L. I. Gurvits, Leonid Gurvits +9 · 2 citations
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Cosmic Phenomena #BL Lac object #Blazar #Brightness #Brightness temperature #Galaxy #Gamma ray #Physics #Radio Astronomy Observations and Technology #Redshift #Superconducting and THz Device Technology #Very-long-baseline interferometry #astro-ph
paper · pdf · doi:10.1093/pasj/52.6.975
8 pages, 8 figures, to appear in Publ. Astron. Soc. Japan
arxiv created 2000/07/24 · openalex publication_date 2000/12/01 · arxiv updated 2015/06/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Abstract 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 1999 January-February. 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>5.8×1013 K for the rest-frame brightness temperature of the core, which is the highest value measured with VSOP to date.