Letter to the Editor

A rapid and dramatic outburst in Blazar 3C 454.3 during May 2005

Optical and infrared observations with REM and AIT

¹ Dipartimento di Fisica e Osservatorio Astronomico, Università di Perugia, via A. Pascoli, 06123 Perugia, Italy e-mail: lars.fuhrmann@fisica.unipg.it
² INAF, Osservatorio Astronomico di Torino, via Osservatorio 20, 10025 Pino Torinese (TO), Italy
³ Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, PA 16802, USA
⁴ Tuorla Astronomical Observatory, University of Turku, Väisäläntie 20, 21500 Piikkiö, Finland
⁵ INAF, Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate (Lc), Italy
⁶ Universitá degli studi di Milano-Bicocca, Dipartimento di Fisica, Piazza delle Scienza 3, 20126 Milan, Italy
⁷ INAF, Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34131 Trieste, Italy
⁸ Dunsink Observatory, Castleknock Dublin 15, Ireland
⁹ INAF, Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio Catone, Italy
¹⁰ INAF, Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy
¹¹ IASF/CNR, Sezione di Palermo, via Ugo La Malfa 153, 90146 Palermo, Italy
¹² IASF/CNR, Sezione di Bologna, via Gobetti 101, 40129 Bologna, Italy

Received: 28 September 2005
Accepted: 8 October 2005

Abstract

The flat-spectrum radio quasar 3C 454.3 is well known to be a highly active and variable source with outbursts occurring across the whole electromagnetic spectrum over the last decades. In spring 2005, 3C 454.3 has been reported to exhibit a strong optical outburst which subsequently triggered multi-frequency observations of the source covering the radio up to γ-ray bands. Here, we present first results of our near-IR/optical (V, R, I, H band) photometry performed between May 11 and August 5, 2005 with the Rapid Eye Mount (REM) at La Silla in Chile and the Automatic Imaging Telescope (AIT) of the Perugia University Observatory. 3C 454.3 was observed during an exceptional and historical high state with a subsequent decrease in brightness over our 86 days observing period. The continuum spectral behaviour during the flaring and declining phase suggests a synchrotron peak below the near-IR band as well as a geometrical origin of the variations e.g. due to changes in the direction of forward beaming.