GAMMA-RAY LIGHT CURVES AND VARIABILITY OF BRIGHT FERMI-DETECTED BLAZARS

By A. Abdo, M. Ackermann, M. Ajello, E. Antolini, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini and 161 more. 2010

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This paper presents light curves as well as the first systematic characterization of variability of the 106 objects in the high-confidence Fermi Large Area Telescope Bright AGN Sample (LBAS). Weekly light curves of this sample, obtained during the first 11 months of the Fermi survey (2008 August 4–2009 July 4), are tested for variability and their properties are quantified through autocorrelation function and structure function analysis. For the brightest sources, 3 or 4 day binned light curves are extracted in order to determine power density spectra (PDSs) and to fit the temporal structure of major flares. More than 50% of the sources are found to be variable with high significance, where high states do not exceed 1/4 of the total observation range. Variation amplitudes are larger for flat spectrum radio quasars and low/intermediate synchrotron frequency peaked BL Lac objects. Autocorrelation timescales derived from weekly light curves vary from four to a dozen of weeks. Variable sources of the sample have weekly and 3–4 day bin light curves that can be described by 1/fα PDS, and show two kinds of gamma-ray variability: (1) rather constant baseline with sporadic flaring activity characterized by flatter PDS slopes resembling flickering and red noise with occasional intermittence and (2)—measured for a few blazars showing strong activity—complex and structured temporal profiles characterized by long-term memory and steeper PDS slopes, reflecting a random walk underlying mechanism. The average slope of the PDS of the brightest 22 FSRQs and of the 6 brightest BL Lacs is 1.5 and 1.7, respectively. The study of temporal profiles of well-resolved flares observed in the 10 brightest LBAS sources shows that they generally have symmetric profiles and that their total duration vary between 10 and 100 days. Results presented here can assist in source class recognition for unidentified sources and can serve as reference for more detailed analysis of the brightest gamma-ray blazars.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/d0f65fa93e9e504b63daf55560e98908ff3857ba

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Citations in the corpus

A method for the estimation of the significance of cross-correlations in unevenly sampled red-noise time series (2014, background): “…in blazars and other AGNs is a simple power-law power spectral density (PSD ∝ 1/νβ ), as has been measured for a small number of sources at various wavelengths (e.g. Hufnagel & Bregman 1992; Edelson et al. 1995; Uttley et al. 2003; Arévalo et al. 2008; Chatterjee et al. 2008; Abdo et al. 2010).”
LOCATION OF γ-RAY FLARE EMISSION IN THE JET OF THE BL LACERTAE OBJECT OJ287 MORE THAN 14 pc FROM THE CENTRAL ENGINE (2010, methodology): “We measured the flux in 7-day bins and fixed the slope of the photon spectrum of OJ287 at−2.4, (as determined over the first 11 months of LAT observations by Abdo et al. 2010b).”
Detection of significant cm to sub-mm band radio and γ-ray correlated variability in Fermi bright blazars (2014, background): “For instance, the joint occurrence of a γ-ray flare and an optical polarization position angle swing observed in 3C 279 provides evidence for co-spatial emission regions along a curved trajectory at a significant distance from the central engine (Abdo et al. 2010b).”
THE FIRST CATALOG OF ACTIVE GALACTIC NUCLEI DETECTED BY THE FERMI LARGE AREA TELESCOPE (2010, methodology): “This source is associated with M82, also known as NGC 3034 and 3C 231, a starburst galaxy previously detected by the LAT (Abdo et al. 2010d).”
Non-thermal particle acceleration in collisionless relativistic electron-proton reconnection (2016, background): “In addition to the distributed, and relatively steady, blazar emission discussed above, blazars often exhibit intense, rapid flares in gamma rays (Abdo et al. 2010, 2011; Aharonian et al. 2007).”