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

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2019-12
Major/Subject
Mcode
Degree programme
Language
en
Pages
17
5300-5316
Series
Monthly Notices of the Royal Astronomical Society, Volume 490, issue 4
Abstract
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.
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Keywords
radiation mechanisms: non-thermal, galaxies: individual: CTA 102, galaxies: jets, galaxies: nuclei, gamma-rays: general, SWIFT, VARIABILITY, TELESCOPE, BLAZARS, FERMI, OBJECTS, CALIBRATION, RADIATION, FLARES, SCALE
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Citation
Lähteenmäki, A, Tammi, J, Tornikoski, M, Hovatta, T, WEBT Collaboration & OVRO Team 2019, ' Investigating the multiwavelength behaviour of the flat spectrum radio quasar CTA 102 during 2013-2017 ', Monthly Notices of the Royal Astronomical Society, vol. 490, no. 4, pp. 5300-5316 . https://doi.org/10.1093/mnras/stz2792