1 2009 Fermi Symposium, Washington, D.C., Nov. 2-5 arXiv:1001.1563v1 [astro-ph.CO] 10 Jan 2010 eConf C091122 ∗ The F-GAMMA team (in alphabetical order): E. Angelakis, L. Fuhrmann, T. P. Krichbaum, S. Larsson, N. Marchili, G. Nestoras, H. Ungerechts, and J. A. Zensus et al. $^{1}$http://pulsar.sternwarte.uni-erlangen.de/tanami/ As of December 2009, the data collected include: Swift , Fermi LAT, and APEX preliminary results (see Table I). The preliminary APEX flux density pre- sented here was provided by the F-GAMMA team, and the final data calibration is in process. The TANAMI and CHI simultaneous datasets will be cor- related shortly. To illustrate the radio morphology at parsec-scales, we show two TANAMI VLBI im- ages of PKS 2052 − 47 obtained in February 2008 at 8 and 22 GHz (Ojha et al., submitted to A&A, and Kadler et al. in preparation) in Figure 1. Notice that the image resolution of the 8 GHz map is higher than that at 22 GHz, due to the inclusion of a telescope in Chile, equipped only with a receiver at 8 GHz, provid- ing longer baselines to better resolve the source. From July 2009, the Automatic Telescope for Op- tical Monitoring (ATOM) team reported a steady increase of flux density from PKS 2052-47, which reached its high state and flared in the optical band in August [6]. Right after this, the Fermi Large Area Telescope (LAT) observed a gamma-ray flare from this source [7]. To understand the physics at work and emission mechanisms during its flaring state, we ar- ranged a multi-wavelength campaign from radio to gamma-ray in early September 2009 in order to fol- low its active phase. PKS 2052 − 47 is a flat-spectrum radio quasar with a redshift of 1.489 [1]. Earlier Australia Telescope Com- pact Array (ATCA) and Chandra X-ray observations showed that the source has a two-sided jet at kilopar- sec scales in the radio band, with no extended emis- sion in X-rays [2]. Very Large Baseline Interferometry (VLBI) observations by TANAMI 1 (Tracking Active Galactic Nuclei with Austral Milliarcsecond Interfer- ometry, see [3–5]) show that the parsec-scale structure is very compact, with a high brightness-temperature core of 2 × 10 $^{12}$K and a size of (0 . 3 × 0 . 1) mas at 8.4 GHz. At 22 GHz the source is unresolved with a restoring beam of (1 . 9 × 1 . 3) mas. At 8.4 GHz, a very faint jet to the west is seen (see Figure 1). The multiwavelength campaign of PKS 2052 − 47 was arranged simultaneously with the scheduled southern VLBI observations of TANAMI during early September 2009. The observation log is re- ported in Table I. The participating facilities in- clude: Ceduna-Hobart Interferometer (CHI), the large APEX bolometer camera (LABOCA) [8] at the Ata- cama Pathfinder EXperiment (APEX, in the frame- work of the F-GAMMA project, see [9]), the Ultra- Violet/Optical Telescope (UVOT) and X-Ray Tele- scope (XRT) onboard Swift , and the Fermi Large Area Telescope. The Swift target-of-opportunity ob- servations covered five days centered at the date of the TANAMI observations, and the exposure time for each observation was between 1500 and 2500 seconds. The flat-spectrum radio quasar PKS 2052 − 47 experienced an optical flare in July − August, 2009. On August 9, the LAT detector onboard Fermi observed a flare from the source, which reached its active phase in the following two months. To further investigate the physics and emission mechanisms during the flaring state of this source, we arranged a multiwavelength campaign from radio to gamma-ray to study its spectral energy distribution (SED) and its brightness variations across the spectrum. Here we present the first results of this multiwavelength campaign. C. S. Chang $^{1}$, E. Ros1 , $^{2}$, M. Kadler3 , 4 , $^{5}$, R. Ojha6 , $^{7}$, the Fermi LAT Collaboration, the TANAMI team, and the F-GAMMA team ∗ $^{1}$Max-Planck-Institut f¨ur Radioastronomie, Auf dem H¨ugel69, D-53121 Bonn, Germany $^{2}$Departament d’Astronomia i Astrof´ısica, Universitat de V al` encia, E-46100 Burjassot, Spain $^{3}$Dr. Remeis-Sternwarte & ECAP, Sternwartstr. 7, D-96049 Bamberg, Germany $^{4}$CRESST/NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA $^{5}$USRA, 10211 Wincopin Circle, Suite 500 Columbia, MD 21044, USA $^{6}$USNO, 3450 Massachusetts Ave., NW, Washington DC 20392, USA and $^{7}$NVI, Inc., 7257D Hanover Parkway, Greenbelt, MD 20770, USA Multiwavelength campaign of the gamma-ray flaring source PKS 2052 − 47 2. Multiwavelength observations 1. Introduction 3. Preliminary results