A Decade of Multiwavelength Observations of the TeV Blazar 1ES 1215+303: Extreme Shift of the Synchrotron Peak Frequency and Long-term Optical–Gamma-Ray Flux Increase

Creators: Valverde, Janeth; Horan, Deirdre; Bernard, Denis; Fegan, Stephen; Abeysekara, A. U.; Archer, A.; Benbow, W.; Bird, R.; Brill, A.; Brose, R.; Buchovecky, M.; Buckley, J. H.; Christiansen, J. L.; Cui, W.; Falcone, A.; Feng, Q.; Finley, J. P.; Fortson, L.; Furniss, A.; Gent, A.; Gillanders, G. H.; Giuri, C.; Gueta, O.; Hanna, D.; Hassan, T.; Hervet, O.; Holder, J.; Hughes, G.; Humensky, T. B.; Kaaret, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Krause, M.; Krennrich, F.; Lang, M. J.; Maier, G.; Moriarty, P.; Mukherjee, R.; Nieto, D.; Nievas-Rosillo, M.; O'Brien, S.; Ong, R. A.; Otte, A. N.; Park, N.; Petrashyk, A.; Pfrang, K.; Pichel, A.; Pohl, M.; Prado, R. R.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Ribeiro, D.; Richards, G. T.; Roache, E.; Sadeh, I.; Santander, M.; Scott, S. S.; Sembroski, G. H.; Shahinyan, K.; Shang, R.; Sushch, I.; Vassiliev, V. V.; Weinstein, A.; Wells, R. M.; Wilcox, P.; Wilhelm, A.; Williams, D. A.; Williamson, T. J; Noto, Giuliana; Edwards, P. G.; Piner, B. G.; Ramazani, V. Fallah; Hovatta, T.; Jormanainen, J.; Lindfors, E.; Nilsson, K.; Takalo, L.; Kovalev, Y. Y.; Lister, M. L.; Pushkarev, A. B.; Savolainen, T.; Kiehlmann, S.; Max-Moerbeck, W.; Readhead, A. C. S.; Lähteenmäki, A.; Tornikoski, M.; Fermi-LAT Collaboration; VERITAS Collaboration

Abstract

Blazars are known for their variability on a wide range of timescales at all wavelengths. Most studies of TeV gamma-ray blazars focus on short timescales, especially during flares. With a decade of observations from the Fermi-LAT and VERITAS, we present an extensive study of the long-term multiwavelength radio-to-gamma-ray flux-density variability, with the addition of a couple of short-time radio-structure and optical polarization observations of the blazar 1ES 1215+303 (z = 0.130), with a focus on its gamma-ray emission from 100 MeV to 30 TeV. Multiple strong GeV gamma-ray flares, a long-term increase in the gamma-ray and optical flux baseline, and a linear correlation between these two bands are observed over the ten-year period. Typical HBL behaviors are identified in the radio morphology and broadband spectrum of the source. Three stationary features in the innermost jet are resolved by Very Long Baseline Array at 43.1, 22.2, and 15.3 GHz. We employ a two-component synchrotron self-Compton model to describe different flux states of the source, including the epoch during which an extreme shift in energy of the synchrotron peak frequency from infrared to soft X-rays is observed.

Additional Information

© 2020 The American Astronomical Society. Received 2019 October 2; Accepted 2020 February 7; Published 2020 March 17. The Fermi-LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States; the Commissariat à l'Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucléaire et de Physique des Particules in France; the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy; the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK), and Japan Aerospace Exploration Agency (JAXA) in Japan; and the KA Wallenberg Foundation, the Swedish Research Council, and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d'Études Spatiales in France. This work performed in part under DOE Contract DE- AC02-76SF00515. This research is supported by grants from the U.S. Department of Energy Office of Science, the U.S. National Science Foundation and the Smithsonian Institution, and by NSERC in Canada. This research used resources provided by the Open Science Grid, which is supported by the National Science Foundation and the U.S. Department of Energy's Office of Science, and resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under Contract No. DE-AC02-05CH11231. We acknowledge the excellent work of the technical support staff at the Fred Lawrence Whipple Observatory and at the collaborating institutions in the construction and operation of VERITAS. This research has made use of data from the MOJAVE database, which is maintained by the MOJAVE team (Lister et al. 2018). The MOJAVE program is supported under NASA-Fermi grant NNX15AU76G. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This research has made use of data from the OVRO 40 m monitoring program (Richards et al. 2011), which is supported in part by NASA grants NNX08AW31G, NNX11A043G, and NNX14AQ89G, as well as by NSF grants AST-0808050 and AST-1109911. J.V. was partially supported by the Alliance program, a partnership between Columbia University, NY, USA, and three major French institutions: École Polytechnique, Paris 1 Panthéon-Sorbonne University, and Science Po. T.S. was supported by the Academy of Finland projects 274477, 284495, and 312496. W.M. acknowledge support from CONICYT project Basal AFB-170002. Y.Y.K. and A.B.P. were supported by the Russian Foundation for Basic Research (project 17-02-00197), the government of the Russian Federation (agreement 05.Y09.21.0018), and the Alexander von Humboldt Foundation. S.K. acknowledges support from the European Research Council under the European Union's Horizon 2020 research and innovation program, under grant agreement No 771282. Software: AIPS (Greisen 2003), DIFMAP (Shepherd 1997), Fermi Science Tools (Fermi Science Support development team 2019).

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