The simultaneous low state spectral energy distribution of 1ES 2344+514 from radio to very high energies^⋆

¹ IFAE, Edifici Cn., Campus UAB, 08193 Bellaterra, Spain
² INAF National Institute for Astrophysics, 00136 Rome, Italy
³ Università di Siena, and INFN Pisa, 53100 Siena, Italy
⁴ Universidad Complutense, 28040 Madrid, Spain
⁵ Technische Universität Dortmund, 44221 Dortmund, Germany
⁶ Max-Planck-Institut für Physik, 80805 München, Germany
⁷ University of Łódź, 90236 Lodz, Poland
⁸ Inst. de Astrofísica de Canarias, 38200, La Laguna, Tenerife, Spain
⁹ Depto. de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Spain
¹⁰ Deutsches Elektronen-Synchrotron (DESY), 15738 Zeuthen, Germany
¹¹ ETH Zurich, 8093 Zurich, Switzerland
¹² Universität Würzburg, 97074 Würzburg, Germany
¹³ Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, 28040 Madrid, Spain
¹⁴ Università di Udine, and INFN Trieste, 33100 Udine, Italy
¹⁵ Inst. de Astrofísica de Andalucía (CSIC), 18080 Granada, Spain
¹⁶ Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka and University of Split, 10000 Zagreb, Croatia
¹⁷ Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
¹⁸ Institut de Ciències de l’Espai (IEEC-CSIC), 08193 Bellaterra, Spain
¹⁹ Tuorla Observatory, University of Turku, 21500 Piikkiö, Finland
²⁰ Japanese MAGIC Consortium, Division of Physics and Astronomy, Kyoto University, Japan
²¹ Inst. for Nucl. Research and Nucl. Energy, 1784 Sofia, Bulgaria
²² Universitat de Barcelona (ICC/IEEC), 08028 Barcelona, Spain
²³ Università di Padova and INFN, 35131 Padova, Italy
²⁴ INAF/Osservatorio Astronomico and INFN, 34143 Trieste, Italy
²⁵ Università dell’Insubria, Como, 22100 Como, Italy
²⁶ Università di Pisa, and INFN Pisa, 56126 Pisa, Italy
²⁷ ICREA, 08010 Barcelona, Spain
²⁸ now at École polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland
²⁹ supported by INFN Padova  
³⁰ now at: DESY, Zeuthen, Germany
³¹ now at: Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Finland
³² also at Instituto de Fisica Teorica, UAM/CSIC, 28049 Madrid, Spain
³³ Università di Trieste, and INFN Trieste, 34127 Trieste, Italy
³⁴ Agenzia Spaziale Italiana (ASI) Science Data Center, 00044 Frascati, and INAF-Oar, 00040 Monteporzio Catone, Italy
³⁵ INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, 90146 Palermo, Italy
³⁶ INFN Padova, 35131 Padova, Italy
³⁷ Max-Planck-Institut für Radioastronomie, 53121 Bonn, Germany
³⁸ Instituto de Radio Astronoma Milimétrica, 18012 Granada, Spain
³⁹ Crimean Astrophysical Observatory, 98409 Nauchny, Ukraine
⁴⁰ Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
⁴¹ Department of Physics and Astronomy, Western Kentucky University, Bowling Green, KY 42103, USA
⁴² Astro Space Center of Lebedev Physical Institute, 117997 Moscow, Russia
⁴³ Dr. Remeis-Sternwarte and ECAP, Universität Erlangen-Nürnberg, 96049 Bamberg, Germany
⁴⁴ Universities Space Research Association, Columbia, MD 21044, USA
⁴⁵ Aalto University Metsähovi Radio Observatory, 02540 Kylmälä, Finland
⁴⁶ Department of Physics, Purdue University, West Lafayette, IN 47906, USA
⁴⁷ Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA
⁴⁸ Pulkovo Observatory, 196140 St. Petersburg, Russia
⁴⁹ Sternberg Astronomical Institute, Moscow State University, 119992 Moscow, Russia
⁵⁰ Theoretische Physik IV, Ruhr-Universität Bochum, 44780 Bochum, Germany

Received: 9 November 2012
Accepted: 22 April 2013

Abstract

Context. BL Lacertae objects are variable at all energy bands on time scales down to minutes. To construct and interpret their spectral energy distribution (SED), simultaneous broad-band observations are mandatory. Up to now, the number of objects studied during such campaigns is very limited and biased towards high flux states.

Aims. We present the results of a dedicated multi-wavelength study of the high-frequency peaked BL Lacertae (HBL) object and known TeV emitter 1ES 2344+514 by means of a pre-organised campaign.

Methods. The observations were conducted during simultaneous visibility windows of MAGIC and AGILE in late 2008. The measurements were complemented by Metsähovi, RATAN-600, KVA+Tuorla, Swift and VLBA pointings. Additional coverage was provided by the ongoing long-term F-GAMMA and MOJAVE programs, the OVRO 40-m and CrAO telescopes as well as the Fermi satellite. The obtained SEDs are modelled using a one-zone as well as a self-consistent two-zone synchrotron self-Compton model.

Results. 1ES 2344+514 was found at very low flux states in both X-rays and very high energy gamma rays. Variability was detected in the low frequency radio and X-ray bands only, where for the latter a small flare was observed. The X-ray flare was possibly caused by shock acceleration characterised by similar cooling and acceleration time scales. MOJAVE VLBA monitoring reveals a static jet whose components are stable over time scales of eleven years, contrary to previous findings. There appears to be no significant correlation between the 15 GHz and R-band monitoring light curves. The observations presented here constitute the first multi-wavelength campaign on 1ES 2344+514 from radio to VHE energies and one of the few simultaneous SEDs during low activity states. The quasi-simultaneous Fermi-LAT data poses some challenges for SED modelling, but in general the SEDs are described well by both applied models. The resulting parameters are typical for TeV emitting HBLs. Consequently it remains unclear whether a so-called quiescent state was found in this campaign.