Multifrequency monitoring of the blazar 0716+714 during the GASP-WEBT-AGILE campaign of 2007

A&A 481, L79-L82 (2008)
DOI: 10.1051/0004-6361:200809552

Letter

Multifrequency monitoring of the blazar 0716+714 during the GASP-WEBT-AGILE campaign of 2007

M. Villata¹, C. M. Raiteri¹, V. M. Larionov^{2, 3}, O. M. Kurtanidze^{4, 5, 6}, K. Nilsson⁷, M. F. Aller⁸, M. Tornikoski⁹, A. Volvach¹⁰, H. D. Aller⁸, A. A. Arkharov³, U. Bach¹¹, P. Beltrame¹², G. Bhatta¹³, C. S. Buemi¹⁴, M. Böttcher¹⁵, P. Calcidese¹⁶, D. Carosati¹⁷, A. J. Castro-Tirado¹⁸, D. Da Rio¹², A. Di Paola¹⁹, M. Dolci²⁰, E. Forné²¹, A. Frasca¹⁴, V. A. Hagen-Thorn², J. Heidt⁶, D. Hiriart²², M. Jelínek¹⁸, G. N. Kimeridze⁴, T. S. Konstantinova², E. N. Kopatskaya², L. Lanteri¹, P. Leto²³, R. Ligustri¹², E. Lindfors⁷, A. Lähteenmäki⁹, E. Marilli¹⁴, E. Nieppola⁹, M. G. Nikolashvili⁴, M. Pasanen⁷, B. Ragozzine¹⁵, J. A. Ros²¹, L. A. Sigua⁴, R. L. Smart¹, M. Sorcia²², L. O. Takalo⁷, M. Tavani²⁴, C. Trigilio¹⁴, R. Turchetti¹², K. Uckert¹⁵, G. Umana¹⁴, S. Vercellone²⁵, and J. R. Webb¹³

¹ INAF, Osservatorio Astronomico di Torino, Italy
e-mail: villata@oato.inaf.it
² Astronomical Institute, St.-Petersburg State University, Russia
³ Pulkovo Observatory, Russia
⁴ Abastumani Astrophysical Observatory, Georgia
⁵ Astrophysikalisches Institut Potsdam, Germany
⁶ Landessternwarte Heidelberg-Königstuhl, Germany
⁷ Tuorla Observatory, University of Turku, Finland
⁸ Department of Astronomy, University of Michigan, MI, USA
⁹ Metsähovi Radio Obs., Helsinki Univ. of Tech. TKK, Finland
¹⁰ Radio Astronomy Lab. of Crimean Astrophysical Obs., Ukraine
¹¹ Max-Planck-Institut für Radioastronomie, Germany
¹² Circolo Astrofili Talmassons, Italy
¹³ SARA Observatory, Florida International University, FL, USA
¹⁴ INAF, Osservatorio Astrofisico di Catania, Italy
¹⁵ Astrophys. Inst., Dept. of Phys. & Astron., Ohio Univ., OH, USA
¹⁶ Oss. Astronomico della Regione Autonoma Valle d'Aosta, Italy
¹⁷ Armenzano Astronomical Observatory, Italy
¹⁸ Instituto de Astrofísica de Andalucía, CSIC, Spain
¹⁹ INAF, Osservatorio Astronomico di Roma, Italy
²⁰ INAF, Osservatorio Astronomico di Teramo, Italy
²¹ Agrupació Astronòmica de Sabadell, Spain
²² Instituto de Astronomía, UNAM, Mexico
²³ INAF, Istituto di Radioastronomia Sezione di Noto, Italy
²⁴ INAF, IASF-Roma, Italy
²⁵ INAF, IASF-Milano, Italy

(Received 11 February 2008 / Accepted 15 February 2008)

Abstract
Aims. Since the CGRO operation in 1991-2000, one of the primary unresolved questions about the blazar $\gamma$ -ray emission has been its possible correlation with the low-energy (in particular optical) emission. To help answer this problem, the Whole Earth Blazar Telescope (WEBT) consortium has organized the GLAST-AGILE Support Program (GASP) to provide the optical-to-radio monitoring data to be compared with the $\gamma$ -ray detections by the AGILE and GLAST satellites. This new WEBT project started in early September 2007, just before a strong $\gamma$ -ray detection of 0716+714 by AGILE.
Methods. We present the GASP-WEBT optical and radio light curves of this blazar obtained in July-November 2007, about various AGILE pointings at the source. We construct NIR-to-UV spectral energy distributions (SEDs), by assembling GASP-WEBT data together with UV data from the Swift ToO observations of late October.
Results. We observe a contemporaneous optical-radio outburst, which is a rare and interesting phenomenon in blazars. The shape of the SEDs during the outburst appears peculiarly wavy because of an optical excess and a UV drop-and-rise. The optical light curve is well sampled during the AGILE pointings, showing prominent and sharp flares. A future cross-correlation analysis of the optical and AGILE data will shed light on the expected relationship between these flares and the $\gamma$ -ray events.

Key words: galaxies: active -- galaxies: BL Lacertae objects: general -- galaxies: BL Lacertae objects: individual: S5 0716+71 -- galaxies: jets