Long-term optical variability properties of blazars in the SDSS Stripe 82

Mao, Lili; Zhang, Xuemei

doi:10.1007/s10509-016-2934-6

Cited by 9 publications

(8 citation statements)

References 119 publications

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“…This can occur if the FSRQs showing RWB trends have been observed in their faint state and contain a significant contribution of thermal emission from the disc, whereas FSRQs showing BWB trends have been observed in the bright state when they are completely dominated by non-thermal jet emission, as are BL Lacs. Another study by Mao & Zhang (2016) on 29 Blazars, consisting of 25 BL Lacs and only 4 FSRQs found that 17 out of 25 BL Lacs and 2 out of 4 FSRQs showed a significant BWB trend in their stripe 82 observational periods, whereas 1 FSRQ followed an RWB trend. They propose that the BWB trend is quite common in long-term optical light curves of BL Lacs while an RWB trend in FSRQs is attributed to the thermal emission from the accretion disc.…”

Section: Discussionmentioning

confidence: 94%

“…Optical flux and colour variability long have been a subject of blazar research, with many attempts made to study the origin of their flux variations. Multiple studies have investigated the colour behaviour of the blazars using different blazar samples and individual blazars over different timescales (e.g., Vagnetti et al 2003;Gu et al 2006;Rani et al 2010;Ikejiri et al 2011;Mao & Zhang 2016). However, due to the lack of reasonably unbiased and large samples, the universality in their colour behaviour has been highly debated.…”

Section: Discussionmentioning

confidence: 99%

“…The study of blazar variability is an important tool that provides valuable information about their nature. The optical variability of blazars has been a topic of intensive research since their discovery as it affords a unique perspective on accretion disc and jet physics (Wagner & Witzel 1995;Ghosh et al 2000;Villata et al 2004;Gupta et al 2008;Rani et al 2010;Ikejiri et al 2011;Gu & Ai 2011;Bonning et al 2012;Mao & Zhang 2016). In particular, optical brightness variations in blazars are often accompanied by spectral variations that can be revealed by the colour-magnitude (or spectral index-magnitude) correlations (e.g., Ciprini et al 2003).…”

Section: Introductionmentioning

confidence: 99%

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Optical Flux and Colour Variability of Blazars in the ZTF Survey

Negi,

Joshi,

Chand

et al. 2021

Preprint

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We investigate the temporal and colour variability of 897 blazars, comprising 455 BL Lacertae objects (BL Lacs) and 442 Flat Spectrum Radio Quasars (FSRQs), selected from the Roma-BZCAT catalogue, using the multi-band light curves from the Zwicky Transient Facility (ZTF DR6) survey. Assessing the colour variability characteristics over ∼2 year timescales, we found that 18.5 per cent (84 out of 455) BL Lacs showed a stronger bluer when brighter (BWB) trend, whereas 9.0 per cent (41 out of 455) showed a redder when brighter (RWB) trend. The majority (70 per cent) of the BL Lacs showing RWB are host galaxy dominated. For the FSRQ subclass, 10.2 per cent (45 out of 442) objects showed a strong BWB trend and 17.6 per cent (78 out of 442) showed a strong RWB trend. Hence we find that BL Lacs more commonly follow a BWB trend than do FSRQs. This can be attributed to the more dominant jet emission in the case of BL Lacs and the contribution of thermal emission from the accretion disc for FSRQs. In analysing the colour behaviour on shorter time windows, we find many blazars evince shorter partial trends of BWB or RWB nature (or occasionally both). Some of such complex colour behaviours observed in the colour-magnitude diagrams of the blazars may result from transitions between the jet-dominated state to the disc-dominated state and vice versa.

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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optical Flux and Colour Variability of Blazars in the ZTF Survey

Negi,

Joshi,

Chand

et al. 2021

Preprint

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“…Gu et al 2006 ;Bonning et al 2012 ;Meng et al 2018 ); ho we ver, this is not al w ays the case, as some studies find the reverse or find SWB trends (e.g. Gu & Ai 2011 ;Zhang et al 2015 ;Mao & Zhang 2016 ). Furthermore, while many studies find these simple colour behaviours, some find that the colour trends can be comple x; for e xample, Isler et al ( 2017 ) showed that the B-J colour behaviour of the FSRQ 3C 279 varied on different time-scales, and o v er different periods during the 7 yr of observation.…”

Section: Introductionmentioning

confidence: 88%

Multiwavelength optical and NIR variability analysis of the Blazar PKS 0027-426

Guise

Hönig

Almeyda

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We present multi-wavelength spectral and temporal variability analysis of PKS 0027-426 using optical griz observations from DES (Dark Energy Survey) between 2013-2018 and VOILETTE (VEILS Optical Light curves of Extragalactic TransienT Events) between 2018-2019 and near infrared (NIR) JKs observations from VEILS (VISTA Extragalactic Infrared Legacy Survey) between 2017-2019. Multiple methods of cross-correlation of each combination of light curve provides measurements of possible lags between optical-optical, optical-NIR, and NIR-NIR emission, for each observation season and for the entire observational period. Inter-band time lag measurements consistently suggest either simultaneous emission or delays between emission regions on timescales smaller than the cadences of observations. The colour-magnitude relation between each combination of filters was also studied to determine the spectral behaviour of PKS 0027-426. Our results demonstrate complex colour behaviour that changes between bluer when brighter (BWB), stable when brighter (SWB) and redder when brighter (RWB) trends over different timescales and using different combinations of optical filters. Additional analysis of the optical spectra is performed to provide further understanding of this complex spectral behaviour.

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“…They are emitters of broad electromagnetic spectrum from radio to γ-rays. The spectral energy distribution (SED) of blazars is characterized by two well-defined broad humps: one at the infrared-optical/UV frequencies and the other at hard X-ray-γ-ray frequencies [1]. The lowenergy hump is due to synchrotron radiation in the jet.…”

Section: Introductionmentioning

confidence: 99%

Multi-frequency variabilities: blazar classification and statistical properties

Yoyponsan

Sawangwit

Komonjinda

2023

J. Phys.: Conf. Ser.

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Blazars are a class of active galactic nuclei whose jets are aligned with the observer’s line of sight. They are powerful multi-frequency emitters that exhibit rapid and violent variation. Classification of blazars requires multi-frequency observation which may be able to achieve through careful planning. However, in the age of automated surveys, we might be able to complete the same task via data mining and machine learning. In this work, we explore the possibility of using the data from robotic surveys for blazar classifications, particularly the variability of their multi-frequency light curves. The 5 th edition of the Roma-BZCAT is used as our reference blazar catalog. The optical light curves of blazar studied here are taken from the Zwicky Transient Facility (ZTF) public Data Release 4 (2018-2020). The distributions of variability and fractional variability amplitudes in g and r bands are presented and compared for BL Lacs and FSRQs. The Principle Component Analysis (PCA) is then applied to various features extracted from the discrete correlation function (DCF) between the two bands as well as the variability and fractional variability amplitudes of the two bands. Although, our machine learning application for the the BL Lac-FSRQ classification shows unpromising result, the PCA has shown that around 80% of the populations can be explained with 13 features which mainly are the DCF-based ones.

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Long-term optical variability properties of blazars in the SDSS Stripe 82

Cited by 9 publications

References 119 publications

Optical Flux and Colour Variability of Blazars in the ZTF Survey

Optical Flux and Colour Variability of Blazars in the ZTF Survey

Multiwavelength optical and NIR variability analysis of the Blazar PKS 0027-426

Multi-frequency variabilities: blazar classification and statistical properties

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