Correlation Analysis of Delays between Variations of Gamma-Ray and Optical Light Curves of Blazars

DOI: 
10.3390/galaxies4040064
Publication date: 
23/11/2016
Main author: 
Williamson, Karen
IAA authors: 
Agudo, Iván; Casadio, Carolina; Gómez, José; Molina, Sol
Authors: 
Williamson, Karen; Jorstad, Svetlana; Marscher, Alan; Larionov, Valeri; Agudo, Iván; Arkharov, Arkady; Blinov, Dmitry; Casadio, Carolina; Gómez, José; Hagen-Thorn, Vladimir; Joshi, Manasvita; Konstantinova, Tatiana; Kopatskaya, Evgenia; Larionova, Elena; Larionova, Liudmilla; Malmrose, Michael; McHardy, Ian; Molina, Sol; Morozova, Daria; Taylor, Brian Troitsky, Ivan
Journal: 
Galaxies
Publication type: 
Article
Volume: 
4
Pages: 
64
Issue: 
4
Abstract: 
<p>We have been performing multi-wavelength monitoring of a sample of <span class="MathJax" data-mathml="&lt;math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot; display=&quot;inline&quot;&gt;&lt;semantics&gt;&lt;mi mathvariant=&quot;sans-serif&quot;&gt;&amp;#x3B3;&lt;/mi&gt;&lt;/semantics&gt;&lt;/math&gt;" id="MathJax-Element-1-Frame" role="presentation" style="position: relative;" tabindex="0"><nobr><span class="math" id="MathJax-Span-1" role="math" style="width: 0.635em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.492em; height: 0px; font-size: 125%;"><span style="position: absolute; clip: rect(1.108em, 1000.49em, 2.477em, -1000em); top: -2.092em; left: 0em;"><span class="mrow" id="MathJax-Span-2"><span class="semantics" id="MathJax-Span-3"><span class="mi" id="MathJax-Span-4"><span style="font-family: &quot;Arial Unicode MS&quot;,serif; font-size: 80%; font-style: normal; font-weight: normal;">γ</span></span></span></span></span></span></span></nobr></span> -ray blazars since the launch of the <i>Fermi Gamma-ray Space Telescope</i> in 2008. We present <span class="MathJax" data-mathml="&lt;math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot; display=&quot;inline&quot;&gt;&lt;semantics&gt;&lt;mi mathvariant=&quot;sans-serif&quot;&gt;&amp;#x3B3;&lt;/mi&gt;&lt;/semantics&gt;&lt;/math&gt;" id="MathJax-Element-2-Frame" role="presentation" style="position: relative;" tabindex="0"><nobr><span class="math" id="MathJax-Span-5" role="math" style="width: 0.635em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.492em; height: 0px; font-size: 125%;"><span style="position: absolute; clip: rect(1.108em, 1000.49em, 2.477em, -1000em); top: -2.092em; left: 0em;"><span class="mrow" id="MathJax-Span-6"><span class="semantics" id="MathJax-Span-7"><span class="mi" id="MathJax-Span-8"><span style="font-family: &quot;Arial Unicode MS&quot;,serif; font-size: 80%; font-style: normal; font-weight: normal;">γ</span></span></span></span></span></span></span></nobr></span> -ray and optical light curves for several quasars and BL Lac objects from the sample to illustrate different patterns of variability. We investigate correlations between <span class="MathJax" data-mathml="&lt;math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot; display=&quot;inline&quot;&gt;&lt;semantics&gt;&lt;mi mathvariant=&quot;sans-serif&quot;&gt;&amp;#x3B3;&lt;/mi&gt;&lt;/semantics&gt;&lt;/math&gt;" id="MathJax-Element-3-Frame" role="presentation" style="position: relative;" tabindex="0"><nobr><span class="math" id="MathJax-Span-9" role="math" style="width: 0.635em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.492em; height: 0px; font-size: 125%;"><span style="position: absolute; clip: rect(1.108em, 1000.49em, 2.477em, -1000em); top: -2.092em; left: 0em;"><span class="mrow" id="MathJax-Span-10"><span class="semantics" id="MathJax-Span-11"><span class="mi" id="MathJax-Span-12"><span style="font-family: &quot;Arial Unicode MS&quot;,serif; font-size: 80%; font-style: normal; font-weight: normal;">γ</span></span></span></span></span></span></span></nobr></span> -ray and R-band light curves and, if these are statistically significant, determine delays between variations at the two wavebands. Such time delays can reveal the relative locations of the emitting regions in AGN jets and the origin of the high-energy photons. We present preliminary results of this analysis. Of the 29 blazars with sufficient time coverage, 17 display a significant, singular, correlated time lag when tested over the entire 7-year period. Of these sources, the six that exhibit a consistent time lag across a majority of epochs of high activity have lags of 0 ± 7 days; the 11 without consistency across epochs of high activity generally display longer mean lags, with <span class="MathJax" data-mathml="&lt;math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot; display=&quot;inline&quot;&gt;&lt;semantics&gt;&lt;mi mathvariant=&quot;sans-serif&quot;&gt;&amp;#x3B3;&lt;/mi&gt;&lt;/semantics&gt;&lt;/math&gt;" id="MathJax-Element-4-Frame" role="presentation" style="position: relative;" tabindex="0"><nobr><span class="math" id="MathJax-Span-13" role="math" style="width: 0.635em; display: inline-block;"><span style="display: inline-block; position: relative; width: 0.492em; height: 0px; font-size: 125%;"><span style="position: absolute; clip: rect(1.108em, 1000.49em, 2.477em, -1000em); top: -2.092em; left: 0em;"><span class="mrow" id="MathJax-Span-14"><span class="semantics" id="MathJax-Span-15"><span class="mi" id="MathJax-Span-16"><span style="font-family: &quot;Arial Unicode MS&quot;,serif; font-size: 80%; font-style: normal; font-weight: normal;">γ</span></span></span></span></span></span></span></nobr></span> -ray leading optical. Eleven sources display no significant singular correlation over either the entire 7-year period or across shorter intervals. No significant difference is apparent between the BL Lac objects and FSRQs. Even after 7 years of monitoring, our correlation analysis remains plagued with uncertainties due to insufficient data.</p>
Database: 
ADS
URL: 
http://www.mdpi.com/2075-4434/4/4/64
ADS Bibcode: 
2016Galax...4...64W
Keywords: 
galaxies:active; galaxies: jets; quasars: general; BL Lacertae objects: general