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GASP observation of a spectacular optical-to-radio brightening of the blazar AO 0235+16

ATel #1724; M. Villata and C. M. Raiteri (INAF, Osservatorio Astronomico di Torino, Italy), D. Carosati (Armenzano Astronomical Observatory, Italy), W. P. Chen and E. Koptelova (Institute of Astronomy, National Central University, Taiwan), V. M. Larionov, D. Gorshanov, T. S. Konstantinova, E. N. Kopatskaya, and L. Larionova (Astronomical Institute, St.-Petersburg State University, Russia, and Pulkovo Observatory, Russia), K. Nilsson and M. Pasanen (Tuorla Observatory, University of Turku, Finland), M. A. Gurwell (Harvard-Smithsonian Center for Astrophysics, MA, USA), P. Leto (INAF, Istituto di Radioastronomia Sezione di Noto, Italy), C. S. Buemi, C. Trigilio, and G. Umana (INAF, Osservatorio Astrofisico di Catania, Italy), M. F. Aller and H. D. Aller (Department of Astronomy, University of Michigan, MI, USA), for the GASP Collaboration
on 19 Sep 2008; 14:23 UT
Credential Certification: Claudia M. Raiteri (raiteri@oato.inaf.it)

Subjects: Radio, Millimeter, Infra-Red, Optical, AGN

Referred to by ATel #: 1735, 1744, 1785, 1849

The GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) reports on the recent observation of a spectacular optical-to-radio brightening of the blazar AO 0235+16, reaching levels comparable to those of the 2006-2007 outburst (see Raiteri et al. 2008, A&A, 480, 339). On August 12, 2008, the source was at R ~ 17.5 and brightened by 1 mag in the next 3 days; after an oscillating and increasing trend it was at R ~ 16.1 on September 8, and a further brightening led to R ~ 14.75 on September 17.8, followed by a slight dimming to R ~ 15.1 at September 18.0. Last night (September 18-19) the level was more or less the same, but the bright close Moon prevented precise measurements. The same behaviour has been observed in the near-IR (Campo Imperatore), with the September 18.0 peak at J ~ 12.55. At mm wavelengths (SMA), the source has been around 3 Jy in the last 30 days, and previously showed a progressive flux increase from the base level of ~ 0.5 Jy following the 2006-2007 outburst. Similarly, at 43 GHz (Noto) and 14.5-4.8 GHz (UMRAO) the source brightened from about 1 Jy in early 2008 to 4-5 Jy and 3.5-2.5 Jy, respectively, in mid 2008, then remaining in a bright state.