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Stochastic approach to modeling the γ-ray variability of Fermi/LAT blazars

Published online by Cambridge University Press:  24 March 2015

M. Sobolewska ,
A. Siemiginowska ,
B. Kelly  and
K. Nalewajko
M. Sobolewska
Affiliation:
Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland email: [email protected]
A. Siemiginowska
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
B. Kelly
Affiliation:
Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106-9530, USA
K. Nalewajko
Affiliation:
Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road M/S 29, Menlo Park, CA 94025, USA NASA Einstein Postdoctoral Fellow
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Abstract

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We studied the γ-ray variability of 13 blazars observed with the Fermi Large Area Telescope (LAT). These blazars were among the brightest ones monitored during the first 4 years of the Fermi sky survey. We modelled their γ-ray light curves with the Ornstein-Uhlenbeck (OU) process or mixed OU process. The power spectral density (PSD) of the OU process is a zero-centered Lorentzian function, proportional to 1/fα with α changing at a characteristic time scale, τ0, from 0 (τ ≫ τ0) to 2 (τ ≪ τ0). The PSD of the mixed OU process has in addition an intermediate part with 0 < α < 2 between the long and short characteristic time scales. We show that the OU model provides a good description of the Fermi/LAT light curves of three blazars in our sample. For the first time we provide constraints on the characteristic γ-ray time scale of variability in two BL Lac sources, 3C 66A and PKS 2155-304. We find that the mixed OU process describes the light curves of the remaining 10 blazars better than the OU process. We infer that their Fermi/LAT PSD resemble power-law functions and constrain their PSD slopes.

Keywords

black hole physicsBL Lacertae objects: generalgalaxies: activegalaxies: jetsgamma rays: galaxies
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 10 , Issue S313: Extragalactic jets from every angle , September 2014 , pp. 21 - 26
Copyright
Copyright © International Astronomical Union 2015 

References

Abdo, A. A., Ackermann, M., & Ajello, M., et al. 2010, ApJ, 722, 520CrossRefGoogle Scholar
Axelsson, M., Borgonovo, L., & Larsson, S. 2005, A&A, 438, 999Google Scholar
Belloni, T., Homan, J., Casella, P., et al. 2005, A&A, 440, 207Google Scholar
H. E. S. S. Collaboration, Abramowski, A., Acero, F., et al. 2010, A&A, 520, A83Google Scholar
Kelly, B. C., Bechtold, J., & Siemiginowska, A. 2009, ApJ, 698, 895Google Scholar
Kelly, B. C., Sobolewska, M., & Siemiginowska, A. 2011, ApJ, 730, 52CrossRefGoogle Scholar
Kelly, B. C., Becker, A. C., Sobolewska, M., Siemiginowska, A., & Uttley, P. 2014, ApJ, 788, 33Google Scholar
Markowitz, A., Edelson, R., Vaughan, S., et al. 2003, ApJ, 593, 96Google Scholar
Nakagawa, K. & Mori, M. 2013, ApJ, 773, 177Google Scholar
Nalewajko, K. 2013, MNRAS, 430, 1324Google Scholar
Nolan, P. L., Abdo, A. A., Ackermann, M., et al. 2012, ApJS, 199, 31Google Scholar
Pottschmidt, K., Wilms, J., Nowak, M. A., et al. 2003, A&A, 407, 1039Google Scholar
Reig, P., Papadakis, I. E., Sobolewska, M. A., & Malzac, J. 2013, MNRAS, 435, 3395Google Scholar
Saito, S., Stawarz, Ł., Tanaka, Y. T., et al. 2013 ApJL, 766, LL11CrossRefGoogle Scholar
Sobolewska, M., Siemiginowska, A., Kelly, B., & Nalewajko, K. 2014, ApJ, 786, 143Google Scholar
Spiegelhalter, D. J., Best, N. G., Carlin, B. P., & Van Der Linde, A. 2002, Journal of the Royal Statistical Society: Series B (Statistical Methodology), 64, 583Google Scholar
Uttley, P., McHardy, I. M., & Vaughan, S. 2005, MNRAS, 359, 345Google Scholar