The timescales of the optical variability of blazars. III - OJ 287 and BL Lacertae

Carini, M. T.; Miller, H. R.; Noble, J. C.; Goodrich, Bret

doi:10.1086/116217

Cited by 131 publications

(100 citation statements)

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“…Optical observations can also indicate the possible presence of other components in addition to synchrotron continuum. There is good evidence for the presence of IDV and colour variability in some BL Lacertae objects and our source is among those (e.g., Carini et al 1992, Clements & Carini 2001, Gu et al 2006, H.E.S.S. Collaboration et al 2011).…”

Section: Introductionmentioning

confidence: 53%

“…Due to its pronounced variability over entire electromagnetic spectra it has been continuously monitored with Whole Earth Blazar Telescope (WEBT) 1 since 1997 till today; which involves four major WEBT multi-frequency campaigns, two of them were organized in 1999 supplemented with ASCA and Beppo SAX observations (Ravasio et al 2002) (Villata et al 2002;Böttcher et al 2003;Villata et al 2004a,b). Carini et al (1992) studied two optically bright sources, OJ 287 and BL Lacertae using a decade long photometric observations where they found IDV of the order of 0.08 mag/hr in former and 0.01 mag/hr for later. Authors also detected hints of bluer-whenbrighter (BWB) trend but any relation between spectral and flux changes were absent.…”

Section: Introductionmentioning

confidence: 99%

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Multiband optical variability studies of BL Lacertae

Agarwal¹,

Gupta²

2015

Monthly Notices of the Royal Astronomical Society

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We monitored BL Lacertae for 13 nights in optical B, V, R, and I bands during October and November 2014 including quasi-simultaneous observations in V and R bands using two optical telescopes in India. We have studied multi-band optical flux variations, colour variation and spectral changes in this blazar. Source was found to be active during the whole monitoring period and showed significant intraday variability on 3 nights in V and R filters while displayed hints of variability on 6 other dates in R passband and on 2 nights in V filter. From the colour-magnitude analysis of the source we found that the spectra of the target gets flatter as it becomes brighter on intra-night timescale. Using discrete correlation technique, we found that intraday light curves in both V and R filters are almost consistent and well correlated with each other. We also generated spectral energy distribution (SED) of the target using the B, V, R, and I data sets for all 13 nights which could help us investigate the physical process responsible for the observed variations in BL Lacertae objects. We also discuss possible physical causes of the observed spectral variability.

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Section: Introductionmentioning

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Multiband optical variability studies of BL Lacertae

Agarwal¹,

Gupta²

2015

Monthly Notices of the Royal Astronomical Society

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“…Table 2. Since the color difference between target and star pairs is smaller than 1.5, the variation in air mass during the observation has little effect on DLCs (Carini et al 1992;Stalin et al 2004). We also tried different companion stars, and the final significance of intranight variation is quite robust.…”

Section: Resultsmentioning

confidence: 99%

Intranight optical variability of radio-quiet BL Lacertae objects

Liu¹,

Zhang²,

Zhang³

2015

A&A

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Aims. Intranight variation (or microvariation) is a common phenomenon of radio-loud BL Lac objects. However, it is not clear whether the recently found radio-quiet BL Lac objects have the same properties. The occurrence rate of intranight variation is helpful in distinguishing the mechanism of the continuum of radio-quiet BL Lac objects. Methods. We conducted a photometric monitoring of 8 radio-quiet BL Lac objects by the Xinglong 2.16 m and Lijiang 2.4 m telescopes. The differential light curves are calculated between each target and two comparison stars. To quantify the variation, the significance of variation is examined by a scaled F-test. Results. No significant variation is found in the 11 sessions of light curves of 8 radio-quiet BL Lac objects (one galactic source is excluded). The lack of microvariation in radio-quiet BL Lac objects is consistent with the detection rate of microvariation in normal radio-quiet AGNs, but much lower than for radio-loud AGNs. This result indicates that the continua of the radio-quiet BL Lac objects are not dominated by jets that will induce frequent microvariations.

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“…In several epochs a clear bluer-whenbrighter evolution of the source has been found (Paltani et al 1997), a behaviour that appears to beuniversal in BL Lac objects (see e.g. Carini et al 1992;Ghisellini et al 1997;Raiteri et al 2001;Ikejiri et al 2011).…”

Section: Introductionmentioning

confidence: 94%

Long-term monitoring of PKS 2155−304 with ATOM and H.E.S.S.: investigation of optical/γ-ray correlations in different spectral states

Abramowski¹,

Aharonian²,

Benkhali³

et al. 2014

A&A

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In this paper we report on the analysis of all the available optical and very high-energy γ-ray (>200 GeV) data for the BL Lac object PKS 2155−304, collected simultaneously with the ATOM and H.E.S.S. telescopes from 2007 until 2009. This study also includes X-ray (RXTE, Swift) and highenergy γ-ray (Fermi-LAT) data. During the period analysed, the source was transitioning from its flaring to quiescent optical states, and was characterized by only moderate flux changes at different wavelengths on the timescales of days and months. A flattening of the optical continuum with an increasing optical flux can be noted in the collected dataset, but only occasionally and only at higher flux levels. We did not find any universal relation between the very high-energy γ-ray and optical flux changes on the timescales from days and weeks up to several years. On the other hand, we noted that at higher flux levels the source can follow two distinct tracks in the optical flux-colour diagrams, which seem to be related to distinct γ-ray states of the blazar. The obtained results therefore indicate a complex scaling between the optical and γ-ray emission of PKS 2155−304, with different correlation patterns holding at different epochs, and a γ-ray flux depending on the combination of an optical flux and colour rather than a flux alone.

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The timescales of the optical variability of blazars. III - OJ 287 and BL Lacertae

Cited by 131 publications

References 0 publications

Multiband optical variability studies of BL Lacertae

Multiband optical variability studies of BL Lacertae

Intranight optical variability of radio-quiet BL Lacertae objects

Long-term monitoring of PKS 2155−304 with ATOM and H.E.S.S.: investigation of optical/γ-ray correlations in different spectral states

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