Multifrequency Observations of the Blazar 3C 279 in January 2006

We report first results of a multifrequency campaign from radio to hard X-ray energies of the prominent gamma-ray blazar 3C 279, which was organised around an INTEGRAL ToO observation in January 2006, and triggered on its optical state. The variable blazar was observed at an intermediate optical state, and a well-covered multifrequency spectrum from radio to hard X-ray energies could be derived. The SED shows the typical two-hump shape, the signature of non-thermal synchrotron and inverse-Compton (IC) emission from a relativistic jet. By the significant exposure times of INTEGRAL and Chandra, the IC spectrum (0.3 - 100 keV) was most accurately measured, showing - for the first time - a possible bending. A comparison of this 2006 SED to the one observed in 2003, also centered on an INTEGRAL observation, during an optical low-state, reveals the surprising fact that - despite a significant change at the high-energy synchrotron emission (near-IR/optical/UV) - the rest of the SED remains unchanged. In particular, the low-energy IC emission (X- and hard X-ray energies) remains the same as in 2003, proving that the two emission components do not vary simultaneously, and provides strong constraints on the modelling of the overall emission of 3C 279.Comment: 4 pages, 6 figures; to be published in the Proc. of the 6th INTEGRAL workshop "The Obscured Universe" (Moscow, July 2-8, 2006), eds. S. Grebenev, R. Sunyaev, C. Winkler, ESA SP 622 (2006

Investigating the multiwavelength behaviour of the flat spectrum radio quasar CTA 102 during 2013-2017

We present a multiwavelength study of the flat-spectrum radio quasar CTA 102 during 2013-2017. We use radio-to-optical data obtained by the Whole Earth Blazar Telescope, 15 GHz data from the Owens Valley Radio Observatory, 91 and 103 GHz data from the Atacama Large Millimeter Array, near-infrared data from the Rapid Eye Monitor telescope, as well as data from the Swift (optical-UV and X-rays) and Fermi (gamma-rays) satellites to study flux and spectral variability and the correlation between flux changes at different wavelengths. Unprecedented gamma-ray flaring activity was observed during 2016 November-2017 February, with four major outbursts. A peak flux of (2158 +/- 63) x 10(-8) ph cm(-2) s(-1), corresponding to a luminosity of (2.2 +/- 0.1) x10(50) erg s(-1), was reached on 2016 December 28. These four gamma-ray outbursts have corresponding events in the near-infrared, optical, and UV bands, with the peaks observed at the same time. A general agreement between X-ray and gamma-ray activity is found. The gamma-ray flux variations show a general, strong correlation with the optical ones with no time lag between the two bands and a comparable variability amplitude. This gamma-ray/optical relationship is in agreement with the geometrical model that has successfully explained the low-energy flux and spectral behaviour, suggesting that the long-term flux variations are mainly due to changes in the Doppler factor produced by variations of the viewing angle of the emitting regions. The difference in behaviour between radio and higher energy emission would be ascribed to different viewing angles of the jet regions producing their emission.Peer reviewe

Investigating the Puzzling Synchrotron Behaviour of Mrk 421

We investigate the multiwavelength behaviour of the high-energy peaked BL Lac object (HBL) Mrk 421 at redshift z = 0.031 in the period 2007-2015. We use optical photometric, spectroscopic, and polarimetric data and near-infrared data obtained by 35 observatories participating in the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT), as well as by the Steward Observatory Support of the Fermi Mission. We also employ high-energy data from the Swift (UV and X-rays) satellite to study correlations among emission in different bands.open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Investigating the multiwavelength behaviour of the flat spectrum radio quasar CTA 102 during 2013–2017

We present a multiwavelength study of the flat-spectrum radio quasar CTA 102 during 2013-2017. We use radio-to-optical data obtained by the Whole Earth Blazar Telescope, 15 GHz data from the Owens Valley Radio Observatory, 91 and 103 GHz data from the Atacama Large Millimeter Array, near-infrared data from the Rapid Eye Monitor telescope, as well as data from the Swift (optical-UV and X-rays) and Fermi (gamma-rays) satellites to study flux and spectral variability and the correlation between flux changes at different wavelengths. Unprecedented gamma-ray flaring activity was observed during 2016 November-2017 February, with four major outbursts. A peak flux of (2158 +/- 63) x 10(-8) ph cm(-2) s(-1), corresponding to a luminosity of (2.2 +/- 0.1) x10(50) erg s(-1), was reached on 2016 December 28. These four gamma-ray outbursts have corresponding events in the near-infrared, optical, and UV bands, with the peaks observed at the same time. A general agreement between X-ray and gamma-ray activity is found. The gamma-ray flux variations show a general, strong correlation with the optical ones with no time lag between the two bands and a comparable variability amplitude. This gamma-ray/optical relationship is in agreement with the geometrical model that has successfully explained the low-energy flux and spectral behaviour, suggesting that the long-term flux variations are mainly due to changes in the Doppler factor produced by variations of the viewing angle of the emitting regions. The difference in behaviour between radio and higher energy emission would be ascribed to different viewing angles of the jet regions producing their emission.Bulgarian National Science Fund of the Ministry of Education and Science [DN 08-1/2016, DN 18-13/2017, KP-06-H28/3 (2018)]; Foundation for Research and Technology -Hellas; Max-Planck-Institut fur Extraterrestrische Physik; Shota Rustaveli National Science Foundation [FR/217554/16]; Russian Science FoundationRussian Science Foundation (RSF) [17-12-01029]; Institute of Astronomy and Rozhen National Astronomical Observatory [176011, 176004, 176021]; Ministry of Education, Science and Technological Development of the Republic of Serbia; DGAPA (Universidad Nacional Autonoma de M'exico)Universidad Nacional Autonoma de Mexico; PAPIIT projectPrograma de Apoyo a Proyectos de Investigacion e Innovacion Tecnologica (PAPIIT) [IN114917]; Smithsonian InstitutionSmithsonian Institution; Academia SinicaAcademia Sinica - Taiwan; NASA/Fermi Guest Investigator [NNX12AO93G, NNX15AU81G]; Bulgarian National Science Programme 'Young Scientists and Postdoctoral Students 2019', Bulgarian National Science Fund [DN18-10/2017]; National RI Roadmap Projects [DO1-157/28.08.2018, DO1-153/28.08.2018]; Ministry of Education and Science of the Republic of Bulgaria; Regional Government of the Aosta Valley - 'Research and Education' grants from Fondazione CRT; CONICYT project Basal [AFB-170002]; Russian Government Program of Competitive Growth of Kazan Federal University; National Aeronautics and Space AdministrationNational Aeronautics & Space Administration (NASA); Department of Energy in the United StatesUnited States Department of Energy (DOE); Commissariat a l'Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucleaire et de Physique des Particules in FranceCentre National de la Recherche Scientifique (CNRS); Agenzia Spaziale ItalianaItalian Space Agency; Istituto Nazionale di Fisica Nucleare in ItalyIstituto Nazionale di Fisica Nucleare; Ministry of Education, Culture, Sports, Science and Technology (MEXT)Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT); K. A. Wallenberg FoundationKnut & Alice Wallenberg Foundation; Swedish Research CouncilSwedish Research Council; Swedish National Space Board in Sweden; Istituto Nazionale di Astrofisica in ItalyIstituto Nazionale Astrofisica; Centre National d'Etudes Spatiales in FranceCentre National D'etudes Spatiales; United States Department of Energy (DOE) [DE-AC02-76SF00515]; National Aeronautics & Space Administration (NASA) [NNX08AW31G, NNX11A043G, NNX14AQ89G]; National Science Foundation (NSF) [AST-0808050, AST-1109911]; NASA's Goddard Space Flight CenterThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]