The dual nature of blazar fast variability: Space and ground observations of S5 0716+714

C. M. Raiteri, M. Villata, D. Carosati, E. Benítez, S. O. Kurtanidze, A. C. Gupta, D. O. Mirzaqulov, F. D’Ammando, V. M. Larionov, T. Pursimo, J. A. Acosta-Pulido, G. V. Baida, B. Balmaverde, G. Bonnoli, G. A. Borman, M. I. Carnerero, W. P. Chen, V. Dhiman, A. Di Maggio, S. A. EhgamberdievD. Hiriart, G. N. Kimeridze, O. M. Kurtanidze, C. S. Lin, J. M. Lopez, A. Marchini, K. Matsumoto, R. Mujica, M. Nakamura, A. A. Nikiforova, M. G. Nikolashvili, D. N. Okhmat, J. Otero-Santos, N. Rizzi, T. Sakamoto, E. Semkov, L. A. Sigua, L. Stiaccini, I. S. Troitsky, A. L. Tsai, A. A. Vasilyev, A. V. Zhovtan

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12 Scopus citations


Blazar S5 0716+714 is well-known for its short-term variability, down to intraday time-scales. We here present the 2-min cadence optical light curve obtained by the TESS space telescope in 2019 December-2020 January and analyse the object fast variability with unprecedented sampling. Supporting observations by the Whole Earth Blazar Telescope Collaboration in B, V, R, and I bands allow us to investigate the spectral variability during the TESS pointing. The spectral analysis is further extended in frequency to the UV and X-ray bands with data from the Neil Gehrels Swift Observatory. We develop a new method to unveil the shortest optical variability time-scales. This is based on progressive de-trending of the TESS light curve by means of cubic spline interpolations through the binned fluxes, with decreasing time bins. The de-trended light curves are then analysed with classical tools for time-series analysis (periodogram, autocorrelation, and structure functions). The results show that below 3 d there are significant characteristic variability time-scales of about 1.7, 0.5, and 0.2 d. Variability on time-scales $\lesssim 0.2$ d is strongly chromatic and must be ascribed to intrinsic energetic processes involving emitting regions, likely jet substructures, with dimension less than about 10-3 pc. In contrast, flux changes on time-scales $\gtrsim 0.5$ d are quasi-achromatic and are probably due to Doppler factor changes of geometric origin.

Original languageEnglish
Pages (from-to)1100-1115
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - 1 Feb 2021


  • BL Lacertae objects: general
  • BL Lacertae objects: individual: S5 0716+714
  • galaxies: active
  • galaxies: jets


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