Quasi-simultaneous multicolour optical variability of S5 0716+714

“…Despite it being very common to use C-statistics, de Diego (2010) has pointed out that it has severe problems. F test is thought to be the proper statistics to quantify variability (e.g., de Diego 2010; Joshi et al 2011;Goyal et al 2012;Hu et al 2014;Agarwal & Gupta 2015 , where bl n and * n are the number of degrees of freedom for the blazar and comparison star, respectively ( N 1 n = -), and α is the significance level set as 0.01 (2.6σ). If the average F value is larger than the critical value, the blazar is variable at a confidence level of 99%.…”

Section: Variabilitymentioning

confidence: 99%

“…In order to obtain good S/N, our exposure times were chosen to be from 150 to 400 s. Considering the time interval of 10 minutes within each group (because 10 minutes is a safe time interval to bin data sharing similar flux characteristics), we bin the data in a group of three observations. This method is used only for light curves with more than 9 observations on a given night, n n a in the F-statistics, where k 1 1 n = -(k is the number of groups), N k 2 n = -(N is the number of measurements), and α is the significance level (Hu et al 2014). Our analysis results on IDV are shown in Table 5.…”

Section: Variabilitymentioning

confidence: 99%

“…From our results, the BWB trends on intermediate, short, and intraday timescales support the shock-in-jet model. For long-term timescales, host galaxy effect, Doppler factor variation (Villata et al 2004;Hu et al 2014), and the superposition of different components (Bonning et al 2012;Gaur et al 2015) may cause weak BWB (non-corrected host galaxy contributions) or RWB trends (corrected host galaxy contributions). Moreover, for long-term timescales, the different states with different BWB trends support the result from Anderhub et al (2009) and Acciari et al (2011) that, compared with a low-activity state, "harder when brighter" behavior is more pronounced at a high activity level.…”

Section: Relation Of Color and Magnitudementioning

confidence: 99%

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Multi-Color Optical Monitoring of MRK 501 From 2010 to 2015

Xiong¹,

Zhang²,

Zhang³

et al. 2016

ApJS

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We have monitored the BL Lac object Mrk 501 in the optical V, R, and I bands from 2010 to 2015. For Mrk 501, the presence of a strong host galaxy component can affect the results of photometry. After subtracting the host galaxy contributions, the source shows intraday and long-term variabilities for optical flux and color indices. The average variability amplitudes of the V, R, and I bands are 22.05%, 22.25%, and 23.82%, respectively, and the value of the duty cycle is 14.87%. A minimal variability timescale of 106 minutes is detected. No significant time lag between the V and I bands is found on one night. The bluer-when-brighter (BWB) trend is dominant for Mrk 501 on intermediate, short, and intraday timescales, which supports the shock-in-jet model. For the long timescale, Mrk 501, in different states, can have different BWB trends. The corresponding results for non-correcting host galaxy contributions are also presented.

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“…S5 0716+714 has also been detected by γ-ray instruments such as the Compton EGRET, AGILE, Fermi-LAT satellites and also by the MAGIC Cherenkov telescope (see, e.g., [11][12][13][14] and references therein). In particular, there have been numerous optical microvariability studies of S5 0716+714 which reported many interesting results, including achromatic behavior, red noise-type power spectra, and in some cases, correlation between flux and polarization degree [15][16][17][18]. In this proceeding, we present the summary of our optical microvariability studies on S5 0716+714, over the past few years, based on multifrequency photo-polarimetric Whole Earth Blazar Telescope (WEBT) [18,19] observation campaigns in 2009 and 2014 (the data collected by the WEBT Collaboration are stored in the WEBT archive; for questions regarding their availability, please contact the WEBT President Massimo Villata: villata@oato.inaf.it).…”

Section: Introductionmentioning

confidence: 99%

Investigating the Innermost Jet Structures of Blazar S5 0716+714 Using Uniquely Dense Intra-day Photo-polarimetric Observations

Bhatta

2016

Galaxies

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Abstract:The sub-hour timescale variability commonly observed in blazars-widely known as intra-day or microvariability-has been extensively studied in optical photo-polarimetric bands over the past 25-30 years. In addition, there have been comprehensive theoretical discussions on the topic, with various models and scenarios proposed; however, the phenomenon still remains relatively poorly understood. Here we present the summary of our optical microvariability studies over the past few years based on multi-frequency photo-polarimetric Whole Earth Blazar Telescope (WEBT) observation campaigns. The primary objective of the study was to explore the characteristics of the source microvariability on timescales of a few minutes to a few days using exceptionally dense photo-polarimetric observations. The results show that the source often displays fast variability with an amplitude as large as 0.3 mag within a few hours, as well as color variability on similar time scales often characterized by "bluer-when-brighter" trend. Similarly, the correlation between variability in flux and polarization appears to depend upon the configuration of the optical polarization angle relative to the positional angle of the innermost radio core of the jet. Other fascinating observations include a sudden and temporary disappearance in the observed variability lasting for ∼6 h. In addition, the modeling of individual microflares strongly suggests that the phenomenon of microvariability can be best explained by convolved emission from compact emission sites distributed stochastically in the turbulent jet. Besides, analysis of some of the well resolved micro-flares exhibiting high degrees of polarization points towards a complex magnetic geometry pervading the jet with the possible presence of small-scale regions of highly ordered and enhanced magnetic field similar to so-called "magnetic islands".

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Quasi-simultaneous multicolour optical variability of S5 0716+714

Cited by 46 publications

References 72 publications

Multicolor Optical Monitoring of the Quasar 3C 273 from 2005 to 2016

Multicolor Optical Monitoring of the Quasar 3C 273 from 2005 to 2016

Multi-Color Optical Monitoring of MRK 501 From 2010 to 2015

Investigating the Innermost Jet Structures of Blazar S5 0716+714 Using Uniquely Dense Intra-day Photo-polarimetric Observations

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